# How Light Makes Colors > Every color is made of light. See how red, green and blue light add up to build any color on a screen, and why screens glow instead of stain like paint. - URL: https://codigrate.com/blog/how-light-makes-colors - Published: 2026-06-20 - Category: Color Theory - Theme: [Aurora Borealis](https://codigrate.com/theme?product=aurora-borealis) - Publisher: Codigrate (https://codigrate.com) Picture the northern lights washing across a night sky in slow ribbons of green, violet, and soft red. There is no paint up there and no canvas, just light, glowing in colors that seem to arrive from nowhere. The screen in your hand pulls off the very same trick, only smaller and whenever you ask it to. It does not hold paint or ink. It makes color by giving off light, and once you see how that works, color stops being a mystery and becomes something you can build on purpose. The whole thing comes down to a handful of lights and how brightly each one shines. ## Light Travels As Waves Light moves a bit like ripples spreading across water, in waves. The strength of a wave is what your eye reads as brightness. A strong, vivid wave is bright light. A faint wave is dim light. No wave at all is no light, which your eye reads as black. The aurora is this idea written across the whole sky: gas high in the atmosphere gives off light, and the brighter that light glows the more vividly the night is painted. Hold on to that one idea, because brightness being the strength of a wave is the foundation for everything below. ## A Screen Builds Color From Three Lights Get very close to a screen and each tiny dot, each pixel, is really three even tinier lights sitting side by side: one red, one green, and one blue. They never melt into a new kind of light. They simply shine next to each other, and from a normal distance your eye blends them into a single color. That is why this is called additive color. You start in complete darkness and add light until you reach the color you want. This is the opposite of mixing paint. Paint starts on a white page and grows darker the more you add, because every layer soaks up light. A screen starts black and grows brighter the more you add, because every dot gives light off. The aurora follows the same logic as the screen, a dark sky lit up from nothing, never a bright page stained over. Every color a screen can show is just these three lights at different brightnesses. Hand the screen a recipe for how bright to make red, green, and blue, and it reproduces your exact color every time. That recipe is the RGB value, three numbers from 0 to 255, one for each light, where 0 means a light is off and 255 means it is shining at full strength. ## Turning Each Light Up And Down Here is where it clicks. In the mixer below, each of the three lights is a wave in its own color, and all three sit on the same line so you can watch them stack up. Turning a light up makes its wave glow brighter, turning it down makes it fainter, and at zero the wave is gone. So pure red, written ff0000, is a bright red wave with green and blue gone. A soft, dusty olive like 808000 is a fainter red and green together, with blue gone. Black, 000000, is no light at all, so there are no waves. A dimmer light is simply a fainter wave. Try it below. Type a color or pick one, and watch the three lights inside it brighten and fade as you change it.

Disclaimer: This mixer is a simplified picture made to build intuition, not a precise physics simulation. Read its waves and numbers as a feel for how three lights add up, not as exact real world measurements.

## Adding Lights Together Now to the mixing itself. Bring red and green up together and where their waves overlap your eye reads the pair as yellow, ffff00, even though there is no yellow light anywhere, only red and green shining at once. Bring the blue light up as well and all three together come out as white, ffffff, which is why a screen showing plain white is quietly running all three of its lights at full. Take them all away and you are back to black. Green plus blue gives cyan, red plus blue gives magenta, and every shade in between is just those three dials set to different points. That is exactly what the sky is doing during an aurora. The gases up there give off their own light, oxygen its greens and reds, nitrogen its blues and violets, and your eye adds the whole display together into the colors you finally see. The sky becomes one enormous additive screen, running on the same rules as the one in your pocket: a few lights, each at its own brightness, blended by your eye into a single picture. Once you start thinking in lights instead of paint, every color on a screen becomes a simple question: how bright do you make each one? ## Where This Leaves You That is the quiet engine behind every image you have ever watched glow on a display, and behind every aurora you have ever stopped to watch. No paint, no ink, just a handful of lights leaning on each other in the right amounts. To work with exact values, our [color tool](https://codigrate.com/tools/color) takes any hex code and breaks it down into its RGB, HSL, and other equivalents, so you can move between them with confidence. ## Frequently Asked Questions ### What is additive color? Additive color is how a screen makes color: it starts in complete darkness and adds light until it reaches the color you want. Each pixel is three tiny lights, red, green and blue, shining next to each other, and your eye blends them into one color. It is the opposite of mixing paint, which starts white and grows darker. ### How does a screen make every color from just three lights? By changing how brightly each light shines. Red and green up together read as yellow, all three at full make white, and none at all is black. Green plus blue gives cyan, red plus blue gives magenta, and every shade in between is those three dials set to different points. ### What does an RGB value actually mean? It is the recipe for how bright to make each light: three numbers from 0 to 255, one for red, one for green and one for blue, where 0 means a light is off and 255 means it shines at full strength. Hand a screen that recipe and it reproduces your exact color every time. ### Why do screens glow instead of stain like paint? Because a screen gives off light rather than soaking it up. Paint starts on a white page and grows darker as every layer absorbs light, while a screen starts black and grows brighter as every dot adds light. An aurora follows the same additive logic, a dark sky lit up from nothing.