I'm not a good painter so I won't attempt a paint over, especially of a human face. I can give 2 cents in text though... his expression is more akin to "solemn determination" than "anger". When someone is really angry, the flesh between their eyebrow really do bunch up a lot, and even if they aren't speaking or yelling, their eyes would be quite open and appear big because they are probably thinking really hard about bad things happening to the cause of their problem. They might bite their lower lips, and their nostrils might be enlarged due to heavy breathing.
Those are for if you don't want to use the usual red = anger color scheme, and want to keep the purple.