It really depends.. Color, patterns don't really matter. I used to have a Picasso Perc with a regular Occ, Onyx Perc with Snowflake and currently have Blacker Ice pair.
Most people will advise you to put in the smaller clown first then the bigger clown. IME, It really depends on the bigger female. Even if she is added first, if she accepts the male, she will pair up. If she doesn't, she will reject it, perhaps kill it or just leave him alone.
IMO, it is up to the female.