Skin discolouration

My husband has Psoriasis he manages it well and applies creams and moisturisers daily however, unlike the patches on his upper body and buttocks which fade and return but leave the skin clear the patches on his legs are a different matter he has large patches of deep red and brown skin. As mentioned he does moisturise daily but what he needs is a cream that will deal with the skin discolouration. Can anyone help. With thanks