I noticed that on pseudo color visuals XAllocNamedColor(..."green")
fails when there are no more color cells available.
Is there a function that returns the best match that is available in
For example a colormap has 4 color cells, allocated: black, white, blue, green
XAllocNamedColor(..."light green"...) should then return "green" instead
of reporting that "light green" could not be allocated.