I have medium to dark brown hair. Is the light or dark better? I’m afraid the dark may be too dark. I also have olive skin tone.

I’d go for the dark. Visually it reads a dark brown, not black, and eyebrows usually look better if they’re a little darker than your hair.

does it have a true taupe color for blondes?

I'm a dark blonde so it's perfect for me.

What color does light mean? I have dark brown hair and a fair complexion. Would I use light or dark?

I have light brown hair with hilights. I always buy the light color. You can darken it by putting more on. I think it would be the safe way to go but with your dark hair, I'm not sure that's the right choice. Sorry, I'm not much help.

Description is unclear. Does this contain a growth serum or is it just cosmetic.

This product shapes, fills in gaps and covers scars; provides long lasting wear and won't dust off. To help restore your sparse brows, use GrandeBROW Serum at night. Simply sweep this clear serum over your brows and in 4-6 weeks you see an improved appearance of your natural brows.