I think I’ve just found the perfect gift for Matt. I want to vomit every time I see one of his photos with that yellow tinge and I’m sure his colorblindness doesn’t help the situation any, but I think this will seal the deal. The Lumiquest Soft Screen is a cheapish diffuser for DSLRs with a pop-up flash. I need to get one for myself, too. It’s only £9.99, but you may be able to rig something up for a lot less.