Affinity Photo 2 gives you the opportunity to digitally simulate the mixing of wet paint applied to a canvas.
The Paint Mixer Brush is pre-loaded with the Foreground colour selected on the Colour panel. As you drag on the page, this colour blends with the colour of pixels underneath the stroke, giving a smudged appearance to the image.
By default, the mixed colour remains on the Paint Mixer Brush. However, the brush can be manually 'cleaned' at any time. As soon as you drag on the page with a clean brush, the brush will pick up the colour directly underneath it.
Alternatively, the mixed colour can be manually removed from the brush at any time and reloaded with the Foreground colour. You can also set this to occur automatically every time you begin a new stroke.