I'd just like to add my part:
I see the wearing of colours as a guide, and representation of the God/Deity followed. Yes these colours should be worn by a cleric of the faith, but I really don't think it should be enforced upon the player. It is their choice how they play their characters at the end of a day.
When playing as Ranéwin, usually she wears something with Red when visiting the temple/Minaret of Symphony, to show respect, and also helps others to see that she is part of Ilsare's church.
This does not mean she is not going to change her garments ever. Sometimes Ranéwin will wear colours she normally wouldn't, but when she does it's not like shes turning her back on her faith or anything.
And there are points with characters, where they would prefer not to noticed, so will cover up representations from time to time (rarely) to avoid confrontations with people/npc's so on.
Wearing colours should still be part of the Dogma, but shouldn't be forced. As it does help create a definition for the deity, and makes spotting clerics of certain faith's very easy. Example I'd give, Celgar - Luncindate, and very very clearly so.....infact, has anyone ever seen him in something other than Blue?
Serissia and Mylindra are two other examples for the church of Rolfirien, so please, do wear your deities colours, but don't feel like you are being poked and prodded constantly not to change your clothing.