@Humblegoat, I'm impressed by your approach to getting the exact colors you are after!
In my case, I initially just wondering if I could use powdered Prang tempera in soap. I had just started soaping. -- I had 3 or 4 micas and then remembered that, by coincidence, a month or so prior, I had run across these giant 1 lb containers of tempera ( yellow, red, blue and green) in my storage. I had bought when my kids were little. So, I started thinking ....
By the time I got responses on this forum - somewhat mixed on the the advisability of using tempera in soap-- I had already tried out the tempera (the green, the red, and the yellow.) But, I had also already ordered enough micas to me a lifetime (although that hasn't stopped me from buying more - this soaping is a true addiction....)
I thought I'd try out that old orange M&P bar made from Prang. It actually feels great. It's super sudsy and creamy. I think sitting around for 21 months has helped it. It also feels pretty moisturizing. The suds is white, so no staining issues, etc. Since I have so much mica, I hadn't really thought of using that tempera any more. But, now that you talk about your experimenting with the color chart, and since I don't think this Prang tempera is harmful, I might just try some color experiments, too. I only tested the Prang in M&P. Itmay just totally morph into something different in cold process, maybe I'll just end up with greyish-brown bars. But, I'm kind of excited about trying to experiment with it!
As to the magenta and cyan, I have wondered why those ink colors aren't called pink and blue. I guess cuz they are not?