Your comments

Ok, this is probably a Linux bug then, as the only way menus are keyboard accessible when editing a file is by pressing F10.
Or grab the colours from the current theme in linux / osx, ie: Cocoa, GTK
To be able to navigate it with the keyboard would be great too. Ie
left: close
right / enter: open
space: toggle
I completely agree that no extra screen real estate need be dedicated to just handles. Just an indication from cursor change on mouse over would be sufficient.
+-0 I'm not going to up or down vote this as I like the minimap without the border, but I'm not opposed to others wanting the border.