This is something I can get behind because that's a good idea.It shouldn't be if it all goes between color: and ;
However, I can't just allow anything; an unfiltered field is potentially exploitable.
The custom title bar already works this way, going between url( and ); and though I have attempted to force change in that field it simply doesn't show up, because it's still all read as part of the background field, no matter how many times I try to close the brackets.
I don't know what we're arguing about. The reason you can't add anything now and fuck with the layout is because there's a check for the input to see if it's valid before it is applied.
REGEX can be used to ensure hex or RGBA syntax (which is probably how I'd do it) but allowing anything is just loco man (just crazy man).
This'll be a thing in Sep7 3.0; hopefully with a color picker and a preview tool, which would be rad.