I would bet that nearly all microphonium blog visitors already know about The Listening Sessions, Dan Richards' fascinating ongoing project in which he classifies mics on a two axis chart of brightness and coloration, among other things.
A lot of people don't quite understand how coloration can be distinct from brightness/darkness, so I will give it a try: Brightness and darkness refer to the relative balance of low vs high frequencies overall, where coloration is the even more complex tonal variations and timbre imparted by the microphone. The brightness/darkness is general, and coloration is more specific. "No" coloration may be thought of as "clinically accurate" which may look good on a graph but not sound all so pleasant. A highly colored mic might be thought of as an effect, where an uncolored one might be used to measure something like the sound level of a loud machine.
In any case here is one of the charts (reversed B&W so you can see it) seen in various discussion groups. Dan Richards Listening Sessions link here. Well worth a visit.
Frankly I think that too much emphasis is put on these attributes in the field, and not enough on other sounds, such as the distortion known as tizz, that affects many microphones and results in what I think are very artificial, exceptionally breathy, hissy female vocals. I've been warned not to point out any specific examples though, so you can listen for yourself. The typical female tizz vocal sounds like a zzzzzzz sound behind the upper registers, and it is quite fatiguing. Perhaps I should find a way to quantify tizz.