How to Use the Affinity Photo Colour Replacement Brush

In this tutorial, I will be explaining how to use the Affinity Photo Colour Replacement Brush. The brush allows you to selectively replace a colour in an image with a different colour. It does this by sampling the area you paint over to determine the colour you want to replace. This sounds simple, and indeed the tool is easy to use, but if you want to achieve good results there are few things you need to know. This article will explain these and help you achieve great results with the Affinity Photo Colour Replacement Brush.

Selecting the Colour Replacement Brush Tool

You will find the Colour Replacement Brush Tool in the Affinity Photo Tools Palette on the left of the interface. The brush is part of a larger group of tools which also includes the Paint Brush Tool and the Pixel Tool. If you haven’t used the Colour Replacement Brush before you will probably find the icon for one of the other tools displayed.

To access the Colour Replacement Brush Tool in the group, click and hold down your mouse button on the currently displayed icon in the Tools Palette. This will expand the group to display the other tools. You can then click on the Colour Replacement Brush to select it.

Selecting the Colour Replacement Brush Tool in the Affinity Photo Tools Palette

Having selected the Colour Replacement Brush Tool, you need to configure it.

Selecting the Replacement Colour

We will start by selecting the new colour to use with the Colour Replacement Brush. The easiest place to do this is in the Swatches Studio Panel. Where you find this depends on how Affinity Photo’s configured, but it’s probably going to be in the top right-hand corner of the interface. If you can’t see the Swatches panel you can check that it’s visible using Affinity Photo’s view menu. Select the View menu and then the Studio option to see all the panels with a tick mark next to the ones that are visible. If you don’t see a tick mark next to Swatches, click on it with your mouse.

You can see an example of the Swatches Studio Panel below.

Affinity Photo Swatches Studio Panel

In the Swatches Studio Panel, you will see the current foreground and background colours (number 1). In the screenshot above, black is the foreground colour and white is the background colour. The Colour Replacement Brush uses the foreground colour as the replacement colour when you paint with. You can switch the foreground and background colours by clicking the small curved arrow to the top right of the two coloured discs.

Lower down in the panel you can see the colour Swatches. Clicking on a colour will select it as the foreground colour. It’s quite possible that you won’t see the colours in your panel. If you don’t, you can change to the colour swatches by clicking the drop-down list (number 2).

With the replacement colour selected we can look at how to use the Colour Replacement Brush tool.

Replacing a Colour with the Colour Replacement Brush Tool

To demonstrate how to use the Colour Replacement Brush tool I’ll be using the following image. This shows a red boat in the docks at Liverpool and I want to change its colour to green.

example image showing a red boat which will have the colour replaced

When I move my mouse pointer over the red boat, the Colour Replacement Brush previews how the colour will look when it’s applied.

example colour replacement brush preview

This provides two useful points of feedback:

  1. It allows you to preview the replacement colour as if you’ve applied it. If you decide the colour doesn’t look right, you can pick a different colour before you start painting.
  2. It allows you to understand how the brush replaces the colour as you move around the object. This is extremely important and allows you to check different areas before trying to replace the colour in that area. For example, in the above screenshot, you can see a preview of the red of the boat replaced by green. As the preview looks good, it’s safe to apply the brush to that area.

Applying the Colour Replacement Brush Tool

But before you start to apply the Colour Replacement Brush tool you should understand that this is a destructive edit. This means the areas where you replace the colour have their pixels directly changed. It’s, therefore, a good idea not to paint directly onto the background image layer. Instead, you should duplicate the image layer. You can do this in the layers Studio Panel by right-clicking on the background image layer and then selecting “Duplicate” from the pop-up menu.

If your image has multiple layers rather than a single background layer, you can create a new Stamp Layer to edit. A Stamp Layer consolidates all the visible layers in an image into a single new layer. You can create this by pressing Shift + Option + Cmd + E on your keyboard (Mac). If you’re using a PC that’s Shift + Ctrl + Alt + E.

When I’m ready to replace the colour of the boat I’ll start by checking sections using the brush preview. If looks like the brush will make an accurate colour replacement I can click to paint in the new colour, but only in that area. When I have finished that area, I can move on to check and paint the next area.

Colour Replacement in progress

Here you can see the colour replacement in progress. Notice that I’ve spilled over into the water on the left side of the boat (indicated by the red arrow). Ideally you should keep as close to the edge of the object as possible to minimise any spill-over. The Colour Replacement Brush is usually quite accurate providing you don’t move the main area of the brush outside of the colour you’re replacing.

If you spot a problem like this when painting, it’s best to undo and repeat the brush stroke. But if you miss the mistake, you can fix the problem later using a mask. I’ll explain how later in this tutorial.

The Sample Continuously Option

In the above example the colour replacement has spilled over into the water, but there’s another difficult area where the same will probably happen.  This is where you see the red of the boat reflected onto the water. If I use the current settings with the Colour Replacement Brush, when I paint over the red reflection it’s likely to also change the colour of the surrounding water. One way I can limit this is by changing the Sample Continuously option for the brush.

You will find the Sample Continuously option in the Affinity Photo Context Sensitive Toolbar at the top of the interface.

Sample continiously option for the colour replacement brush tool

When the Sample Continuously option’s selected in the toolbar, the Colour Replacement Brush will continuously sample colours as you paint using the area at the centre of the brush. It then replaces the sampled colour with the new colour. In an area like the water where the red’s reflected, it’s likely that the brush will also sample the water as I paint. This causes the water to have its colour replaced.

By unchecking the Sample Continuously option, the sample’s only taken when I first click to start painting with the Colour Replacement Brush. This first colour sample then remains in place as I paint until I release the mouse button. This means that I could sample the red reflection and then continue to paint safely over the other areas, without affecting the surrounding water, until I release the mouse button.

Changing the Tolerance of the Colour Replacement Brush

When painting over small areas like the reflection in this image, it can help to zoom in to the area. This allows you to work with greater precision as well as size your brush to fit the area you want to change.

On checking the brush preview before replacing the red reflection, I noticed that I would still affect the blue of the water even though I’m sampling the red. This is because the Tolerance setting of the brush is too high. By reducing the Tolerance setting to around 10% I can prevent the brush from replacing the blue colour of the water whilst allowing it to accurately replace the red.

replacing the colour of the red reflection on the water

Here you can see the result of reducing the Tolerance to 10%. This shows that the red reflections replaced but the adjustment doesn’t affect the blue water. When you use a high Tolerance setting, you replace a wider range of colours with the brush. But when you use a lower Tolerance you replace a narrower range of colours with the brush. The brush preview makes it easier to see this and allows you to adjust the Tolerance to create an accurate colour replacement.

By using a lower Tolerance and turning off the Sample Continuously option I can accurately replace the red of the reflection with green. You can see the result below which looks quite convincing.

red reflection replaced with gree

By painting carefully at full magnification and using the Sample Continuously option, together with the Tolerance adjustment, it’s possible to replace the red of the boat completely with green. Most importantly, the finished image appears completely believable and you would think the boat was green.

red of boat replaced by green using the color replacement brush tool in affinity photo

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Now let’s look at how to clean up the mistake I made when I painted over the water next to the boat.

Cleaning up the Colour Replacement Layer with a Mask

Earlier in the example, I accidentally painted over an area of water next to the boat, turning it green. Ordinarily when doing this I would use the Undo option in Affinity Photo to fix the problem before continuing to paint. But sometimes you don’t notice a problem until later. When this happens, you can use a mask to help repair the problem.

I’ll start by selecting the layer I’ve been working on in the Affinity Photo “Layers” Studio Panel. I can then click on the icon to the bottom of the panel to add a mask layer.

adding a new mask layer to clean up the colour replacement layer

You can see the icon to add the mask indicated by the red arrow (number 1). Clicking this adds a new mask layer to the currently selected layer (number 2).

I can now switch from using the Colour Replacement Brush tool to the Paint Brush Tool in the Affinity Photo Tools Palette. I’ll be using the Paint Brush Tool to paint black onto the mask in the area where I want to hide the colour replacement.

With the brush tool selected, change the foreground paint colour to black in the Swatches Studio Panel.

Now I can paint onto the mask layer in the area where I want to hide the green. If I mistakenly paint over the green of the boat to reveal any red, I can switch to painting with white on the mask by pressing the letter X on my keyboard (my background colour is white and pressing X switches the foreground and background colours).

edge of the boat following the colour replacement clean up

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The trick to making the clean-up work is to paint slowly and use the brush at 100% opacity, with 100% flow and 100% hardness. When you zoom in close to a high magnification like 100% you can mask out the unwanted colour with a high degree of accuracy.

Affinity Photo Colour Replacement Brush Video

It may also help you to see the Affinity Photo Colour Replacement Brush tool in use, so I created the following video to demonstrate this tutorial.

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Using Affinity Photo Colour Replacement Brush Summary

We’ve now looked at the main features of the Colour Replacement Brush in Affinity Photo. The key points to remember when using this brush are:

  • Be sure to work on a copy pixel layer as the Affinity Photo Colour Replacement Brush is a destructive edit.
  • Use the preview feature of the brush to check the colour and replacement accuracy before you start painting.
  • Make use of the Continuous Sample option and Tolerance settings to work with greater precision.
  • If you make any mistakes use the Undo option, but you can always use a mask later to clean-up if you miss one.
  • Be sure to make use the Zoom option to magnify your image whilst working. Zooming also allows you to check and fix any areas where the colour replacement isn’t quite right.
  • Using a hard-edged brush at 100% Opacity can make it easier to replace the colour of an object convincingly.

The Colour Replacement Brush isn’t the only option for replacing the colour of an object in Affinity Photo. It is though an easy tool to use and does make a good job of the colour replacement providing you follow the advice in this tutorial.

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