Please consider using CSS classes instead of inline style tags when styling elements.
An example of where this would take effect would be the 'Network' tab in which the "tr" (table row) tags have their background colors dictated inline rather than by a class:
If you want to open a pull request, we'd be happy to review and maybe merge this for inclusion in the upcoming Pi-hole v5.0.
If you don't have the time for this, I'm afraid that the likeliness of having this added rather soon is degraded as someone of us will have to sit down. In this case, please, provide a full list of places where you would like to see styles being moved over to CSS classes.