Hehe…red blue and yellow paint typically give an ugly brown actually…despite art teachers in school telling you that you could mix all colors with them
As wikipedia say, the primaries in the typical substractive color space are cyan, magenta and yellow, which are basically the the complements to the RGB primary colors:
cyan absorbs red (i.e. can be described as green+blue light)
magenta absorbs green (i.e. can be described as red+blue light)
yellow absorbs blue (i.e. can be described as red+green light)
However, since in reality white light in most cases does not consist of only 3 distinctive colors, cmy black is typically brownish too.