I decided to make some color changes to a scene I was working on and thought I would use the assign custom color feature to store the current values and work from there.
Okay, I added the first one and it went to the expected top-left slot. But when I tried to add a second color, I couldn't figure out how to do it. I thought I could click the apply color icon of, click the custom color slot, and click "Add to Custom Colors." That didn't work -- it only makes the current color the color of the clicked slot (black.) I also thought the "Define Custom Colors" was a button, especially since it had the underscored 'D", but I haven't seen it active yet. The "What is this" seems to explain how I think it would or should work, but it doesn't for me.
Anyway, I'm probably missing something really simple.