There was an old topic about this, can't find it.
It had a link to
this demo I made. Type any valid css color in the box (pink, skyblue etc. and codes like #FF0088).
Basically, the same technique could the used to color the circle and any part(s) of the text individually without having to generate a ton of images.
Basically, you could make it a setting and let the user pick *any* color. The only limitation is that you can't change the duck or the background color without new images.