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Red and green is one of my top favourite colours combination :D.
I don't know what you mean by wet brushes, so probably no. I made this digital in Photoshop as usual.
Thank you Sander :).

Well in Photoshop you can set the brush tool to mixer brush tool which is like the paint is still wet and you can mix while painting. :)

Is this in modern Photoshop setting? I'm still using CS5 which is ancient and I don't know if there's any mixer here. It actually saddens me that it doesn't even have a permanent colour panel, which I know is present in the recent version.