color-defined-p is a compiled Lisp function in `faces.el'.

(color-defined-p COLOR &optional FRAME)

Return non-nil if COLOR is supported 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"), or
the symbol `unspecified'.

This function returns nil if COLOR is the symbol `unspecified',
or one of the strings "unspecified-fg" or "unspecified-bg".

If FRAME is omitted or nil, use the selected frame.