I read the description of what a Feature Color is but couldn't quite visualise it and so applied to a forum to see. I didn't notice anything different until a bit later, when I noticed that the forum title had become slightly inset. I assumed that was a new feature for subcategories in the latest upgrade.

It was only when I applied a green Feature Color to another forum that I saw what was happening. The problem is that the default #ffffff on the default body background #fcfcfc is nearly invisible.

Given that it's not obvious how the Feature Color is used and that anybody wishing to use it is going to have to change its value anyway, wouldn't it be helpful to give it another default color?

I was wondering about this too - what the heck is a Feature Color, and how does it benefit our communities?

A "Feature Color" highlights the forum icon:

That's selected in the forum settings on the "Display Settings" tab.

It's a way to draw attention to a particular Forum.

It also displays in fluid forum view.  

Streams too:

When I noticed it, it was because it added a stripe to the left of the forum title once I had entered the forum:

Obviously, when I had tested it with the default white, it wasn't possible to notice that stripe.