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.
How to use the colour name to hex
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.
Questions
About 148, inherited from X11 and early Netscape rather than designed.
A genuine inconsistency in the inherited set. Nobody reconciled them and now nobody can, without breaking pages.
Both work and resolve identically. CSS accepts either spelling for every grey-related name.
#663399, added to CSS in 2014 in memory of Eric Meyer’s daughter. The only named colour added deliberately.
For prototyping, fine. For designed work use exact values; the names are arbitrary and rarely the colour you meant.