Color schemes silently disabled in source checkout of core

[Rarst]

When using development version of WordPress the admin color scheme feature is silently disabled. There is a check in code for -src in version.

This is highly confusing from developer experience perspective.

It would make sense to me if there were:

• message in profile, informing that color schemes are being disabled
• short explanation inline for the reasons check is being made

[jdgrimes]

This was confusing to me at first as well. A message would have been helpful.

[helen]

Also wanted to note here that I've prompted a few people to take notes for me as they get started with front end dev in core so we can cover ground some of us haven't thought about in a while in a "how to get started" guide for that particular area (notably SCRIPT_DEBUG, RTL, color schemes, media JS, and related tooling). Haven't gotten anything there, but we should probably at least write an initial page for the handbook and fill it out more as we go.