Hello. So I've been on this quest "Canvas the Castle" for a few hours now. I have searched every inch of the castle and can not find any clues. The only clues I've found thus far are the mysterious painting, and the paint brushes in Chanel's room.

Please, no spoilers! All I'm asking for is a little hint as to where I should be looking. I just need a small hint which is why I haven't checked the wiki or anything. I don't want it completely spoiled. So can someone here possibly help me with a small clue on to where I should find the next clue? Thanks!

Since you've found a painting and brushes, do you think there just might be some traces of paint somewhere?

Have you spoken to everyone? Are there any conflicting stories?

Speak to everyone that your journal mentions. From there it will be easier. And as thinzad says, watch out for conflicting statements.
But if you found the brushes, then you probably already spoke to everyone otherwise the "game" wouldn't let you find that clue.

I know which clue are you missing out - I had some troubles with it too. I'll give you only one advice - search again, all over the castle if necessary, switch to 1st person if necessary.