Colourful type from major hospital spoke out with intelligence (4,6)
I believe the answer is:
Here is my best explanation:
'intelligence' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
(Other definitions for grey matter that I've seen before include "Issue lacking clear boundaries", "intellectual capacity?", "Brain tissue", "intelligence", "stuff in the head", "Brains", "The brain?" and "Intelligence; the brain".)