Hi Charly
I suspect you are using the desktop version rather than iPad?
I think most if not all brushes will do what you want by default. If not, turn on “real colour blending”. See the section below from the manual and I hope it will solve your problem:
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Real Color Blending
ArtRage_4_Manua-209
Most digital painting packages blend colors using an RGB color model. This color model is familiar to people who use painting software but does not produce results familiar to people who work with real paint. Real Color Blending mode allows you to change how ArtRage blends color so that it mimics real world pigments more closely.
Real Color Blending mode can be turned on in the color options menu which can be found in the Tools menu or by clicking the Current Color Sample. The Real Color Blending menu item can be turned on or off whenever you wish. Changing it will not affect any of the paint already on the Canvas, but any paint you blend after changing it will blend in the newly selected mode.
The most obvious example of how Real Color Blending changes the paint color can be found when you blend blue and yellow. Using an RGB blending model the resulting blend comes out somewhere between blue and grey. If you tun on Real Color Blending you find that the resulting color is green.
Real Color Blending is great when you are trying to mix colors, especially if you are used to real paint.
Also many of the knives can be loaded with paint and will blend in their style.
I hope this helps
Brett
"You do not suffer because things are impermanent. You suffer because things are impermanent and you think they are permanent." ~ Thich Nhat Hanh
Tech stuff: 24" iMac M1: Wacom Intuos Pro L: iPad Pro 12.9"