What happens when you pile every color onto one spot?
Look at all these colors… red, green, and blue. Over here they are glowing lights in a dark room. Now they are sliding closer, closer, all onto one little spot. So tell me… when every light lands on the same spot, do you think it goes nice and bright… or does it go dark? Tap your guess, and let’s watch!
After you watchWhat happens when you pile every color onto one spot?
The short answer
When you pile all three colored lights onto one spot they make white, but when you smoosh all three paints together they make brown. Lights glow and pile up, so adding more makes the spot brighter and brighter until it is white. Paints soak up light, so each one you add makes the blob darker and darker until it is brown.
Try this next
- What if you leave one color out? Pile up only red and green lights, leaving blue off, and guess the color before you peek — does it still climb toward bright, or land on a brand-new color?
- What if the room is bright instead of dark? Shine a little flashlight on white paper in a dark closet, then in a sunny window, and guess which one shows the glow better before you check.
The whole story
How it works
Lights and paints play opposite games. A light gives off a glow, so it starts dark and gets brighter every time you add a color — red plus green plus blue lights pile up all the way to white. A paint soaks up some of the light and shows you the leftover, so it starts on white paper and gets darker every time you add a color — red plus green plus blue paints sink all the way to muddy brown.
What people get wrong
It is easy to think more colors must always make a mess, the way smooshing all your paints makes brown. But lights do the opposite. Pile up colored lights and they get brighter, not darker, landing on white instead of brown.
The catch
Lights can glow all the way to bright white, but they need a dark room to show off and a battery or plug to glow. Paints work anywhere, even in daylight with no battery, but they can only ever get darker, so you can never mix your way up to white.
Questions kids ask
Why do the lights go white but the paints go brown?
Lights glow, so when red, green and blue lights pile onto one spot their glows add up and the spot gets brighter and brighter, all the way to white. Paints soak up light, so each paint you add takes more away, and three together leave almost nothing but a dark muddy brown.
If you keep mixing more paints, can you ever get white?
No. Each paint can only soak up more light, never add it back, so every blob makes the mix darker. You can mix your way down to brown, but you can never mix paints up to white.
Where can I see lights make white at home?
Tiny red, green and blue dots on a phone or TV screen glow side by side to make white. Up close you can sometimes spot the little colored dots; from far away your eyes pile them together into white.
Talk about it
- Guess first: if we squeeze every paint we own onto one spot, what color do we get?
- Where have you seen lots of colored lights glow together and look white?
- What do you think is different about how a light makes color and how a crayon makes color?
For grown-ups
This is additive (light) versus subtractive (pigment) color mixing. Red, green and blue light add together because they each give off light, stimulating all three cone types in the eye at once, which we see as white. Pigments instead absorb part of the spectrum and reflect the rest, so combining many of them reflects very little light and looks dark brown — which is why printers use cyan, magenta and yellow inks plus a separate black.
Keep going
What else makes you wonder?
- If three lights make white, what do just red and green lights make with no blue?
- When a screen shows you brown, is it adding light or taking it away?
- What color do you get if you mix only two of the paints instead of all three?