How to keyframe the colour of simple blocks now?

For a quick & dirty sketch, I want to add two simple coloured rectangles to a video and change their colour over time. Until recently, I would've done so by simply making a matte, masking it, then keyframing the colour via the effects (properties) panel, but there's no colour to be found there anymore. Moreover, though you can change a matte's colour, you can't keyframe that. (Maybe using lumetri settings, but that seems overcomplicating things, all I need is just some red to some blue or green). And no, it shouldn't be necessary to move to After FX for something this simple either, right?

Has the implementation for graphics changed (I know it did for titles... a few times), am I looking in the wrong place? I've been using NLEs for 2 decades but never ever had to spend so long trying to find how to do this very simple thing!