What does the rightmost color button do in the Mail > Fonts dialog?

I can't get it to work and I'm not sure why. I’ve started to compose an email.  I press Command-T to bring up the Fonts panel/window. I select some text and then click on the leftmost of the two color buttons in that panel. That brings up the Colors panel. The dropdown is set to ‘Apple’. I click on Orange and my selected text turns orange.

I select some different text and click on the ‘a’ button, the rightmost of the two buttons we’re considering. The Colors panel is already displayed. I click on Cyan in that panel and…nothing happens. The text background color remains white, not Cyan. 

Is there some OK button, or APPLY button I’m missing?

I wonder if I have some option turned on that doesn’t allow the ‘text background’ feature to work.

Ohhh, right--thanks. I mistakenly interpreted dialabrain's message to be saying that the Fonts panel is the one that works, but now I see it's the Format bar that works. Well, that seems to clearly be a bug, but I guess it is what it is.

I actually was hoping for something slightly different: to paint the entire page a certain color, not just the immediate background to the text. With this "text background" feature, all blank lines between paragraphs, as well as left and white margins, remain white. I guess it's not possible to set the page color (or maybe it's called document color?). It seems that it used to be available but was removed some time ago.

I used to set the email page color when I was using Thunderbird for Windows 15 years ago and I really liked that feature.

Can Thunderbird for Mac use the Mac's contact list directly? Last time I looked at it, it seemed that you had to import your contacts into Thunderbird and they wouldn't stay synched.