@billrey the XSI proposal originally had 60+ votes. I based the designed off the original software UI colors which was concealed with a whole army of design experts in their field back in the day.
This XSI theme extensively shows the areas where this was improved (not only on 3D viewport but in many other workspace areas as well). Not only did it serve other users to think about what is really important when viewing vertex on UV layouts or tracks on NLA, but it also is easy on the eyes. First time users find it easy locating important things and experienced users quickly fly through color coded ui by muscle memory (they associate what comes first and what comes after on every step of their 3D tasks).
Please re-consider including the theme. I don´t understand how @Rawalanche comes and states that “it´s a 90’s interface” but doesn´t clearly states why it doesn´t work -regarding UIX-. Because I can post lots of people (including Blender presentations) where it was CRUCIAL for first-time-users to identify things on the UI the way it is on the XSI theme.
From a UIX design point and many other design reasons, the XSI theme has stood the test of time being LEGIBLE in colors as well as long exposed hours in the monitor, identifying crucial elements quickly.
XSI MOD theme was the first one posting this SHADE OF GRAY for the UI way before all the other themes were posted. How can it be removed as -redundant-? The theme was posted, meeting the community guidelines, and was legitimately voted as desired theme to be included.