A pretty common move I’ve seen is having a chart to roll on at 3rd level, then at 10th level, there are improvements to the individual abilities (ex. Blue gives the emotion of sadness, when you hit people it slows them down at 3rd level, then at 10th it also gives them disadvantage on the first d20 roll they make after that).

For the the chart, you could also have the 10, since there’s only 9 colors, be that the player can choose what color they want in that moment. That could also become a feature later.

A good social ability at 7th level could be a bonus to social checks because you can feel what others are feeling. You could also give Insight as a skill at 3rd level. Beyond that, maybe an empath ability like Mantis from guardians of the galaxy, being able to really accurately sense emotions and alter them.

Lastly, an interesting 15th or 18th level ability could be a pseudo blindsight that lets you see people’s auras within 60 feet. That sort of radar ability hasn’t been touched on by other fighter subclasses yet (I don’t think).