Editing Sidebar menu

I am trying to edit the menu on the side for a few things:

I’m categorizing and need the “parent” of each submenu to be bold, so if it would look something like this:

Category 1
–A
–B
Category 2
–A
–B

etc..

And the second thing is I’d also like to change the background color of only the parent to be changed to blue and the background of the submenus to the main menu to be changed to a different color.

Thank you!