You've seen a coupole here now that show a mixed light side of the block.
Here's yet another (shown on the board several times) that shows you can have every block different in darks and lights.
In fact, in this first case (with the pinks) there were some mediums tossed in on each side of the block, too, and it still works well.
The second picture shows a very controlled light/dark color placement.
Jan in VA