It took a bit less work than expected so here is a nice addition to the text elements...
I think the colour picker this is just a functionality that as been removed in a browser update. Even though I can add to the palette, it doesn't remember it in Firefox. I use Chrome as my main browser and there the functionality to add to palette has been removed entirely.
I can see that nice text addition getting some use over the course of time!
I guess that with Chrome at least the temptation to try the pallete option is taken away. Now and then I look to see whether the functionality has come back in Firefox, knowing fairly well that it won't come back.
Would it be a simple addition, while I'm here, to allow a user to right-click on a texture and get the coordinates of that point? I spend quite a lot of the time nudging elements back and forth until they are broadly in the right place and sometimes get the coordinates badly wrong. It would be quite a handy shortcut to right-click on the tail of a Cessna 172 for example, to get a ballpark position for the Cessna logo, and I can them enter those coordinates to get a head start on putting it in the right place.
For example, to enter text on a C172 fuselage the coordinates might be -440,-8, but on the upper tailplane they will be more like 230,-198, and if entering text on the other side of the tailplane the numbers might be something like -608,250 or something like that. So a shortcut right-click (or similar) to get a broad idea would be some help. I certainly don't want you to end up with a repainter tool that can only be operated by rocket scientists that have read a 1000-page manual, but that is something that might mean people with short moments of time can turn around a usable paint.