yes, the broccoli sprouts take a while, but the process is sped up by adding the peroxide. also, the purplish color is normal.
you can dehull the sprouts by putting them in a pot, filling it with water and then swishing the sprouts around. the hulls rise to the top and you can then skim them off. then drain off the sprouts and you will see that some of the hulls fall to the bottom.
are your sprouts getting sunlight? after a few days they need sunlight to mature. that helps them shed the hull also.