Suggestion: hide the recent color area if there is no recent color to show, instead of showing it empty.
I don't think this is a problem. It is so only until the first time you use it and you would know what to expect from the dialog. So if anything then I'd vote for grayed out dialog.
Maybe to show "No recent colors yet" in place of "Recent colors", and hide the blank area beneath.
I think the best procedure here is to hide the section completely when there are no recent colors.
I know you've been very active in the new color-picker tweaks, but--unless you are taking this on now to suppress empty recent colors--please stop moving items that obviously require Design/UX team review back to UI, or to thier specific module, nothing is gained by the thrash.
Back to ux-advise...
(Nothing is gained by making the ux-advise list a clone of libreoffice-bugs: a place to dump tons of bugzilla notifications. *Puh-lease* remove the CC when you’re done with a bug. We’ve given the “UX advise”, so we’re done with this bug.)
Recent colors are an important part of our color pickers. After the latest changes the swatch is filled when you change a color. And last but not least it's not good usability in general to hide things that may become relevant soon.