Random color picker

A color picker that picks. Not a grid of swatches to choose from — a wheel that chooses, which is what you want when the point is to stop deciding: a team color, whose turn it is, what to paint the wall, which pen the class gets today.

Three wheels

This page carries three, and they are all the same tool:

• Red, green and blue — the three lights a screen is made of, and the wheel this page starts on.
• The rainbow — seven colors in the order a prism puts them.
• Every color — twelve, being the ones most people name when asked to name colors.

They are reached by name — ?wheel=rainbow — rather than by the link carrying the colors themselves, and that is not a shortcut. A wheel travels in its link, but color deliberately never does, so a rainbow written out as ordinary slices would arrive in the site's own palette: a rainbow wheel in the wrong colors, which is worse than no rainbow at all. The name stays short, and the colors stay in the file where they belong.

Why red, green and blue?

Because they are the three lights the screen you are reading this on is made of. Every other color here, and every color in every photograph you have ever seen on a display, is those three at different strengths.

So they are the shortest possible answer to pick a color, and they are drawn at full strength rather than tempered into something more tasteful: this is the one wheel on the site that is about its colors, and a slice labelled Red that was drawn a careful brick would be a wheel lying about itself. If three is too few, the rainbow gives you seven and the twelve-color wheel gives you the ones people actually name.

Isn't red next to green a problem?

Yes, and this is the one page on the site that does it anyway. Around 8% of men of European ancestry have some form of red-green color deficiency, as do between 4% and 6.5% of men of Chinese and Japanese ancestry, which is why no palette anywhere else on this site puts those two together.

Here the colors are the subject rather than a way of labelling something, so leaving red or green out would be leaving out part of what the page is for. What holds is the rule underneath: color is never the only channel. Every slice carries its name, the result is announced in words, and the wheel would still be readable in black and white.

Source: Jennifer Birch, “Worldwide prevalence of red-green color deficiency”, Journal of the Optical Society of America A 29(3), 2012, 313–320.

Why does editing the wheel change the colors?

Because the colors belong to the wheel this page ships, not to whatever you build out of it. The three wheels here state their own hex values, which is the only way a wheel about colors can work — a wheel travels in the link, and colors deliberately never do.

Rename a slice and you have your own wheel, and your own wheels take the site's palette, which is chosen to stay legible across a room and to carry no meaning in red against green. Weights are a different matter: lean on the odds all you like and the colors stay, because how a wheel is drawn is not what it weighs.

Every slice is exactly its own chance

Twelve colors means each takes a twelfth of the circle, because each has a one in twelve chance. That is the rule the whole site is built on, and it is why you can trust the picture: there is no setting anywhere that stacks the odds behind slices drawn the same size. The winner is chosen first, by the browser's cryptographic random number generator, and the spin is then solved to land on it — so the animation is a way of showing you an answer that already exists, not a simulation being watched to see what happens.

Type a percentage against a color and the wheel redraws to match, in front of whoever is watching. The full argument for why that matters is on the wheel itself, and the editor below takes any list at all — colors, names, chores, anything — with whatever you build travelling in the link, ready to share by copying the address.