RGB is additive color and CMY(K) is subtractive.
If you built an electronic screen with CMY subpixels, you'd be able to mix colors additively. Cyan + Magenta = Blue, Cyan + Yellow = green, and Magenta + Yellow = Red. Can CMY be additive and RGB be subtractive?
The photo is composed of only Cyan, Magenta, and Yellow pixels (before Stack Exchange's image compression). It appears pixelated/jittered, but a real CMY display would properly reproduce the colors.