Hey there!
Okay, having quite an issue here (though I am using GIMP, not sure if that's the problem inherently), but for whatever reason when I use the eyedropper/colour picker tool no matter where I select I always get the green colour used for the notes (there are some spots in which I can get white however, mostly the die). I've tried messing around with the tool, resetting the software, deleting layers and nothing works. I tried it in Krita and that seems to work fine so this might just be a GIMP problem in which case I have no problems swapping over, just that I'm quite new to digital painting so it's probably just a simple fix. Thanks for reading!