I bought a foundation at Walmart, and wasn't the right color. Will they let me return it or exchange

NO, Unless it was not Opened. BUT if there was no seal on it even if opened just say you didn't lol or, Look for the newbie exchange store worker in the cosmetics section and get them to exchange it. You will be able to exchange it easier than getting your money back. Good Luck also try the Testers/Samplers so you get the Perfect Match next time. :o)