It seems to work fine for me.
I've tried the portable version in Windows 7 and installed versions on two different Windows 10 machines and I can't get text boxes to create with a solid colour properly at all. Either I get no colour whatever I do, or the current colour won't change, or it works fine until I click outside then the background goes transparent. The only way I can make solid colour text boxes is with plain filled rectangles and a separate text box on top.
This is driving me nuts. What am I doing wrong? It never used to be this difficult...?