Colour name to hex

Look up what a CSS colour name resolves to. `orange` is `#ffa500`, `rebeccapurple` is `#663399`, and `gray` and `grey` are the same colour spelled two ways.

The CSS named colours are a historical accident worth understanding before relying on them. They came from the X11 window system by way of early Netscape, and were never designed as a coherent set: `darkgray` is lighter than `gray`, there are four shades of green that are nowhere near each other in the colour space, and the coverage is wildly uneven with dozens of blues and almost no browns. The one deliberate addition is `rebeccapurple`, added to CSS in 2014 in memory of Eric Meyer’s daughter — the only named colour with a story rather than an accident behind it.