You're half way there, marinating for two days is ideal to get real penetration. However, to get that colour deep into the flesh, which is what I think you're after, you have to use the red dye powder from a proper asian store, none of that pansy-ass liquid colouring that granny uses to make nice iced buns with!. It's the only thing that will carry through. You mustn't skip on the quantity either.
When I buy mine from the asian corner shop she gets it from a hidden place under the counter, presumably because it's got lots of nasty chemicals in it! I don't use it much for that very reason.