Return a description of the color named COLOR on frame FRAME.
COLOR should be a string naming a color (e.g. "white"), or a
string specifying a color's RGB components (e.g. "#ff12ec").
Return a list of three integers, (RED GREEN BLUE), each between 0
and either 65280 or 65535 (the maximum depends on the system).
Use `color-name-to-rgb' if you want RGB floating-point values
normalized to 1.0.
If FRAME is omitted or nil, use the selected frame.
If FRAME cannot display COLOR, the value is nil.
COLOR can also be the symbol `unspecified' or one of the strings
"unspecified-fg" or "unspecified-bg", in which case the
return value is nil.