3 Color Operations
A color can be represented in three ways: as a color index (an integer
in 0 to 299, inclusive), as a color name string, or as a rgb
value. All drawing functions which take a color argument accept colors
in any form. An rgb value is assigned to an index with
Takes three values in the range 0 (dark) to 1 (bright) and returns an
rgb (a color).
Changes the color at index in the color table to the
color specified in rgb. Only the first twenty-one indices
are initialized; a color index should not be used until it has
Returns #t if the default display screen for viewports is in
color or #f otherwise.