Regarding color schemes on the RF and HHKB, I prefer a dark (black or graphite) case, but the black on dark-gray keycaps on the black versions of these keyboards seems silly to me -- it's like someone ought to stand up and declare, "The Emperor has no clothes!" To my eye, it would be better to have blanks rather than nearly illegible legends. What is even more comical is that apparently EK made a special arrangement with Topre to correct some issues with the legends for their "EK Edition", which is available only in black!
I like legends, and at times I need them, but I tried populating the entire RF 87 and HHKB with printed caps, and it looked too busy to me. Therefore, on my black RF, I went with printed blue caps for the alphas, spacebar, numbers, and arrow keys, but everything else is black. In addition, I replaced the Windows bubble keys with black Opt/Alt keys from a black HHKB set; they are a perfect match.
On my HHKB, I have done a similar thing, using the lettered white set for the alphas and numbers, keeping everything else (including the spacebar) black.
Now I have a white RF 87u 55g that I was going to use at work, but I don't like the white case. Therefore, I am considering putting it up for sale. It is brand new except for taking it out of the box once to test the keys. Before selling it, I might first take a look to see if I like the effect of putting black mods on it, but I doubt this will look as good as it does on a black case.
I would like to do something similar with the color scheme when I get around to doing a 55g mod on a HHKB, but if I hope to use a Type-S (only available in white), I need to find out if it is possible to move the Type-S switches into a black HHKB case.