Chlorella powder gives a very nice vibrant green, and works better in soap than spirulina on my experience. I also don't like the stink spirulina has. Chlorella doesn't really have a noticeable smell. Maybe a tad chlorophyl-like. It also remains green over time & is less prone to fading than spirulina.
I use a good amount of it when I want a beautiful grass green a deeper leaf green - a good TBSP per kg of soap oils. You could use half that amount or even less for a pale green. It would depend on your base amount of oils.
Peppermint & spearmint work well together. A SMALL amount of wintergreen can also be used to boost this, and I do mean small, as it can become quite unpleasant on the skin in larger amounts. Look into maximum usage amounts for this essential oil. Try anchoring these minty oils with something more earthy. Experiment with what you have on hand to begin with.
It also would depend on the budget you are working with. Some essential oils combine beautifully with peppermint but are more costly, especially if buying in smaller bottles.
You can use any of the above with your base recipe of choice.
