Like with Techmarines--it varies from Chapter to Chapter.
The Codex heavy Chapters go for the flat blue with the left shoulderpad painted in the Chapter's livery.
However, you can do them in your Chapter's livery and do them with some blue accents.
Automatically Appended Next Post: ernshmagl wrote:Paint it the paint scheme as the rest of you army and for the little details pick colors that would make them stand out. For example, i am doing gk and i am doing white and red with gold for the wording and copper for weapons so for me the librarian would follow that same paint scheme because i am in the same boat as you where i want to use a librarian in my army list
Grey Knights are exempt from the whole "Codex Astartes" rulings, but that shouldn't be any real surprise.
With the Grey Knights, no matter what you'd have the steel color and the standard red/white heraldry on parts and the gold detailing.