I can see your point, other characters coming in will be a bit more diverse than say Jax.
However, even in real world scenarios, people dress to match their skin tone, eye color and hair-color, it's a traditional aesthetic fashion choice.
In Jax's case, all that pink is a reflection of her personality, or so I see it. And I think it works in portraying her persona.
That's why it was so exaggerated in her voice, Sandy, a biker... Yeah, vibrant colors don't match her personality. The grounded earthy colors (even her name is a riff off sand) matches her very well I feel!
BUT, the 2 new characters being developed are more diverse in their color scheme!