the color set name, if the parameter value
is an image data, then this function will try to extract the
theme colors from it.
n
number of colors from the given color set(apply cubic
spline for the color sequence), negative value or
ZERO means no cubic spline on the color sequence. [as integer]
character
function returns a color object sequence
or html color code string vector if this parameter
value is set to TRUE. [as boolean]