Consider color-coding token highlights by signal type on hover

[lgessler]

For signals, user gave feedback that it would be nice to color token highlights by type (+ subtype?). E.g., genre = green highlight, DM = yellow highlight, etc.

Solution isn't obvious because we expect token highlights to overlap often. In case of overlap, do colors mix, does the last-applied one win, do we use a "mixed" color...?