I also want to tip my hat to the default theme used on Ubuntu MATE. The desktop's darker backgrounds with white text and colourful icons were much easier on my eyes than the transparent or grey-on-grey themes some projects use. Seeing full, detailed icons rather than vague, abstract shapes was a nice touch too. I feel too many modern themes look like they are designed to intentionally cause eye strain and Ubuntu MATE's high-contrast, colourful look made it easier for me to read the menus and find the controls I wanted to access.
This gets praise for the default theme, although true it is quite good the issue is that light green is not easy on the eye and there is no easy way to escape it completely even after tweaking the theme in the GUI. I like the default theme so essentially I had to edit the metacity-theme-1.xml file and change the color from light green to standard ubuntu orange or dark blue because it is just unusable on old low contrast monitors. For the novice user there should be some way to have a official variation to the default theme - without the light green everywhere in the menues. Is there anyone who would like to vote with me on that?!