I think it's quite easy to implement and it will greatly help coloring compositions – for me these 10 available colors is way too little. I know everyone has own convention of coloring (like, magenta for input nodes, green for output, etc.) but especially because of this fact we need more colors.
Often I need to distinguish green window nodes but I also NEED them to remain green-ish (e.g. for many output windows). If I had, let's say, five tones of green I'd color 5 output windows and distinguish them without changing convention (that green nodes are video outputs). Same with interface nodes – five tones of magenta will allows an user to color keyboard input a little bit differently from mouse input, HIDs and so on. Look at the attached picture – IMO, the lack of colors forces an user to change conventions in the same composition.
Of course, one can have completely different coloring convention – so I think we need about 20-30 colors (4 tones of 5 colors, 5 tones of 6 colors, or something similar). And cascade, two-level tint menu with colors on the first level, and tones of this color on the second level would be perfect!
What do you think, guys?