Lemon-Lime Soap

I decided that I would love to create a lemon-lime soap. I have lemon and lime essential oils, but to make it more interesting it should be swirled with green. I couldn't find a mica or oxide that stayed a true green in cold process soaps and was a non-bleeding color. So, I checked around and read that spirulina powder would give you a dark green color in soap. Perfect!!! I also read that it has a funny smell, but I wasn't really worried because lime and lemon essential oils are pretty strong.

I mixed my soap and at light trace I separated out about 1/3 of my already scented soap and added my spirulina that was premixed with a little olive oil. I mixed it well and the soap was a lovely green color. I poured my main soap, then pour my green soap as you would to swirl it. I use a wooden skewer to drag through the soap and make lovely swirl patterns. The soap smelled and looked wonderful.

I wrapped it up and set it aside thinking "well done" to myself. The next day I pulled my soap out and it still smelled and looked fabulous. I cut and set it to cure. Now, two days later the green has turned to a light brownish-tan color. It still smells great and its actually kind of pretty, but not what I was going for. This is obviously still usable, but not something I'd like to sell.

So I'm not sure what happened. Has anyone else had this problem? Have you use spirulina powder successfully? Like I said, great smell and I can't wait to use it, but I'm curious what went wrong.