Even if it's brown, it could still have dyes in it. They could have dyed it to make it brown, after all. The ingredient list will list any dyes used.All the food is brown. Not multi colored.
If you typically feed just Mazuri, and this is just to act as filler until you get more, it's probably ok. I just wouldn't use it long term as more than 1/4 of what you feed. A few bits here and there shouldn't hurt.