Where can i restyle the admin panel?

I just installed grav + admin panel, where would i be able to customize the admin panel so it is visually different to what it currently looks like.

My plan is to offer a visually edited version of this with themes that are sold for this cms (not selling cms as part of this just themes for ppl to upload for sites build on the program) and wish to add my sites logo and colouring somewhere while still having the grav information on the site.

The plugin Dion linked is a good suggestion, which provides some limited JS-CSS customization.

Admin Pro will be provide “white label” functionality, along with options better suited to be handed out as “your cms” to your clients.