The paper is wet, the colors are deposited and then fuse in damp paper, then begins a dialogue water colors ...
Place on dry paper three colors of your choice ( here we arbitrarily used the three primaries). Wait for their drying complete prior to intervene again to superimpose a different color.
The first color is completely dry, overlay another color preferably transparent. You will get a first mixture optics, and so on. Avoid going beyond three successive overlays to keep the transparency.