Board Thread:Questions and Answers/@comment-108.29.82.182-20130517013930/@comment-5287114-20130520193202

I'm not sure if darker hair is a guaranteed sign of age - some people lose their hair long before others even start to thin, for instance. Remember that Garmadon had brown hair compared to Wu's blonde hair, so perhaps the latter's current form has grey hair to continue the contrast with his younger brother.

Of course, that's just a theory.