Updating the OP with Tone Chroma's colours got me thinking again about what other hues could represent.
Red - Aggressive
Orange - ???
Yellow - Natural
Green - ???
Blue - Old-school
Indigo - ???
Violet - Classical
Pink - ???
My guesses are: green = electronic/experimental, pink = pop, indigo = dark/emo/alt, orange = rap/hip-hop
Of course, it's possible they have no intention of representing some of these colours, and may focus on filling up more options for their current categories - but it's fun to think about!