I was using both Rapidbrow and Rapidlash and noticed a similar discoloration on my eyelid with the lash product, but nothing with the brow product. The discoloration hasn't gone away, but it doesn't bother me. Can camoflage it with eyemakeup or concealer.
However, Rapidbrow and Rapidlash quit working for me, so I switched to GrandeBrow and GrandeLash, after reading raves on HSN. More expensive, but these two REALLY work. Lashes are great, but I especially notice improvement with the brows. The two ends of my brows, near the nose and the tail, have really filled out. I now have to trim brows regularly. Maybe you might like to try.