You can modify the opacity of the assistive ball.
Settings method
realme UI 7.0: Settings > Accessibility & convenience > Assistive Ball > Opacity
realme UI 6.0 & 5.0 & 4.0 & 3.0: Settings >Additional Settings / System settings > Assistive Ball > Opacity
realme UI 2.0 & 1.0: Settings > Convenience tools > Assistive Ball > Transparency of the assistive ball when idling
realme R & Go & S & T & U Edition: not support