I don't have synesthesia to any notable degree but what you're describing kind of makes sense as being it. Not tastes for me, but sounds can elicit such responses eg. a sound having graphite steel I can well imagine. Or other things that would baffle another person.

Frankly, "notes of blue and a hint of graphite steel" sounds too remote from normal experiences to be consciously made up - I mean, who's going to relate to that anyway?