Use icon font for editor icons (may be other icons as well) and changing color will be as simple as setting up css text color property. This approach will force that the icon can only have one color so it is important to have option for image based icons for those who want a multi-color icon.
I hope the editor design remains and ships with the way it looks now. It really does serve as a nice baseline and gives that neutrality which gives off a nice clean look. The editor is now going to be easy to style (with xenforo kindly introducing Style properties) Thanks Mike. So this alone is a bonus to those that want to change the look, xenforo understands that people will want to change it (like they do with node icons) and given us that option.
Already the likes of @Sheldon have posted re-coloured icons. @Luxus as posted a tinymce look and a few others have also posted their enhancements so this alone tells you the visuals can be changed easily with minimum effort. This to me tells me the devs understood that people may want to change the look and given us the option to do so. Easily.
I'll say it again. Excellent work indeed and I personally feel you've done a great job with the editor (with all of 1.2 infact) but especially the editor.
If I had one concern it would be to ship the default editor like in the screenshot (below).