So the primary colors are not Red-Yellow-Blue??!!
  Primary Colors for Color Mixing
Additive
Subtractive
primary colors
Y-M-C
yellow/magenta/cyan
Y + M + C = Black
primary colors
R-G-B
red-blue-green
R + G + B = White
secondary colors
Y-M-C
secondary colors
R-B-G
Demonstrate this:
with 3 slide projectors
Demonstrate this:
with transparencies