-Valid instantiators for color specifiers are:
-
--- a string naming a color (e.g. under X this might be "lightseagreen2"
- or "#F534B2")
--- a color instance (use that instance directly if the device matches,
- or use the string that generated it)
--- a vector of no elements (only on TTY's; this means to set no color
- at all, thus using the "natural" color of the terminal's text)
--- a vector of one or two elements: a face to inherit from, and
- optionally a symbol naming which property of that face to inherit,
- either `foreground' or `background' (if omitted, defaults to the same
- property that this color specifier is used for; if this specifier is
- not part of a face, the instantiator would not be valid)