None of the Claras are wigged--that's their real hair. I thought they were wigged initially, but I saw an article when Katie Clarke first started in the role, and it was her real hair.
And Vicki Clark is actually a redhead and wears a red wig in the show. You can debate on whether it's real or not, but she's most definitely not a brunette.
"Peace! The charm's wound up."
--Macbeth