Mica powder, while gorgeous, does leave a colored ring around your tub. When I make these for myself I don't add any coloring.. but for gifts they're much more pretty!
Tip: use anywhere from 1/8-1/2 teaspoon of mica powder keeping in mind that the more you use the more saturated the water will be with color. Mica powder does leave a ring in the tub.
Not sure where to grab ingredients? Here's a roundup list of my favorite products (and brands) for DIY beauty products and where to buy them!