Many commercial dyes produce weird results over henna. You may get some sort of grey/green yucky color. If you are going blonde, you will be using bleach or color strippers. It is really easy to accidentally turn your hair orange when using bleach, and I'm not sure color strippers work all that well with henna. Also, bleach is really bad for your hair. I recommend asking your local hair salon for a product to strip henna. Most stylists will grimace and say, " Oh, henna, you're screwed! Good luck with that!" but since it has faded you may be able to get most of it out. Personally, I have the same coloring and eyes and I really like http://www.amazon.com/Herbal-Essences-Clairol-Intense-Permanent/dp/B000GCQWFY I use it without beaching first (I have even used it after henna without any scary results). My hair feels really healthy afterwards and the color has really nice highlights in the sun. Also, it fades gradually to a strawberry blonde or red/brown, so it doesn't look weird if you wait a while between dyings.