name->color changes a string name to a color, like this:
> (name->color "lavender")
(make-color 230 230 250)
If you give it a color already, the computer complains:
> (name->color (make-color 230 230 250))
name->color: Expected a string or symbol, but received (make-color 230 230 250 255) colorize changes a name to a color, but does not complain if it gets something that is already a color. That makes it better than name->color.
> (colorize "lavender")
(make-color 230 230 250)
If you give it a color already, the computer complains:
> (colorize (make-color 230 230 250))
(make-color 230 230 250))