Cyan, Magenta and Yellow if it's inks. Red/Yellow/Blue is nonsense really, and Red = Yellow + Magenta
Printers will use black as well though, because the C/M/Y when mixed together give a muddy colour instead of black like it would with pure pigments. That's for subtractive colour mixing anyway.
I prefer Red/Green/Blue though, since that's what I'm more used to using and mixing when picking colours on the computer screen, as computer screens use the primary colours of light
In both those cases though, you can't make every colour in existance, which is why there's also other methods for describing colour space, like L*a*b*.