convert_r_colour_to_magick_colour: Convert an R colour to a magick colour
Description
Convert an R colour to a magick colour
Usage
convert_r_colour_to_magick_colour(col)
Arguments
col
may be a built in colour, like 'tomato' or a hex colour
Value
always returns a hex colour, except if col is NA when it retuns a special
magick colour 'none', which means transparent