Depending on the color and the source if it, colors may morph or fade, but not always. I’d try a tiny batch first, to see. I’ve used some spices like annatto for yellow and that didn’t change.
For hard water, I’d use citric acid in the mix to work as a chelator to reduce the soap scum. Also, use castor oil at 5%, coconut oil at 20%, and 1 tsp of sugar per pound of also in the lye water to really enhance bubbles in any recipe.