The white keys are the ones that are closer to the player's end - and thus easier to reach - of a keyboardy instrument :-)

What I am suggesting is that it is easier to see the principles of modes, when you forget the chromatic scale for a while.

I had old Finnish pentatonic music in mind when I wrote that "...other exotic..." thing; it does not require black keys either. Well, unless you transpose it to Bb, eg... :-)

AKS