I did white, tinted light pinkish ones, and just for the fun if it a few green ones. The green eggs I put in the blue dye and they look pretty not that a green egg really needed any dye.
For years, my brother only had med. brown egg layers. They dyed them and they were a deeper darker color.. Which I found nice... I don't know if they tried it w/ really dark brown eggs.. I would say try it.. Use a wax crayon to decorate them and then do the dying..Report back to us with your results...