I don't understand dark and cold or bright and warm.
I've heard people talk about having a resonant sound and the bell will ring. I never got that top happen. I did get the sound in my head to come out the end of the trumpet.
If I'm reading this correctly, I think I might be able to help on this one.
First, listen to trumpet players that most people would agree that are dark sounding. The two that come quickly to mind is Miles Davis and Ingrid Jensen. Notice that sometimes(especially jensen) have almost a flugelhorn sound to their sound. Not whimpy or weak, but as if someone took the treble out of their sound.
Some examples of bright sounding people would be Doc, MF, Bergeron,.
their sound will peel the paint off the room next door.
Both are very beautiful. I can't think of anything better than Flemenco Sketches by Miles or Teonova by Maynard.
As for the literary description of sound, I think words often fall short when describing music or sound in general. However, poetic descriptions are far better than describing a sound in math, trust me.
Now for resonance:
You might want to read Mark Van Cleave's article on Efficency Through Resonant Intonation. You'll learn the difference between tuning your trumpet and adjusting yourself. Good Luck