a c0ffee lesson

Colors are made of light

Scroll slowly. The panel on the left is your canvas — the words on the right will paint on it. Click any colored word to load it.

Three lights

A screen makes color by shining three lights at every dot: red, green, and blue. You control how brightly each one shines with a number — a color channel — from 0 (off) up to 255 (full).

Turn the red channel all the way up and the others all the way down, and you get a pure, simple .

One for each

The same goes for the others — full green alone is , and full blue alone is .

Watch the left panel as you click each one: only that single channel climbs to full, and the others stay dark.

Adding light up

Here's the surprise. What if we turn everything all the way up at once? We're adding all the colors of light together — and just like sunlight through a prism in reverse, all the light combined makes .

This is why it's called additive color: light adds. That's the opposite of mixing paint, where more colors make things darker and muddier.

And all the way off

So what happens when we turn every channel all the way off? No light at all — which your screen shows as .

Black isn't a color being added; it's the absence of light. White is all three lights at full; black is all three at zero. Every other color lives somewhere in between.

Now you try

You've watched the canvas follow along — now take the wheel.

Try this: on the left panel, drag the red slider down to 0, then nudge green and blue up and down. Notice how every color you can make is just a recipe of three numbers — three lights, added together.

That recipe has a shorthand: the hex code. A color like is just those three channel numbers written in a compact form — but that's a lesson for another cup. ☕