The Big Idea: Your eyes don't have separate detectors for millions of colors. The back of your eye (the retina) has only 3 types of color-sensing cells: Red, Green, and Blue (RGB) cones!
Everyday Analogy
Look closely at your smartphone, TV, or laptop display: every movie scene and photo is made from just tiny Red, Green, and Blue dots placed side-by-side. Your eyes work the exact same way in reverse! When yellow light enters your eye, it stimulates both your red and green cones, and your brain paints the experience of "yellow".
In Luminary: The primary optical channels (Red, Green, Blue) correspond directly to the biological color sensors of the human visual system!
Takeaway: Human vision is an RGB camera system decoded by the brain into 10 million shades.