When you mix the three primary pigment colors together (red (magenta), yellow, blue (cyan)), you get black.
When you mix the three primary light colors together (red, green, blue) you get white.
Additional light sources add light (duh).
Additional pigment sources subtract light.
When you turn on a red subpixel on your monitor and turn on the green subpixel next to it, you're adding the sum of their output up to equal your color.
Red pigment, on the other hand, "eats" all light but red, which it reflects. So they are "subtracting" light from the whole.
So - yea - you're there. ;)