I use a tupperware palette with a wet paper towel in the bottom, and keep it in the fridge when I am not painting--the combination of wet and cold keeps the acrylic from polymerizing so it stays wet and fresh. (This is why house paint tells you to apply it when it is 50 or above--if it's too cold the acrylic won't set up properly. You can't keep the paint in the fridge for more than a week, though, or it gets moldy.
Anyway, foam core is really light, like I said, and I was using a bottle to keep the board from sliding forward when I painted. Then I just had a brain fart and picked up the bottle to clean a brush, and the painting slid forward and pushed the paint palette off the edge of the table, and of course it fell "butter side down". I took a knife and got up most of the paint right away, but I knew the pthalo blue was going to be a problem.
Pthalo blue has tiny, tiny pigment particles and it's both super stable, and really tenacious. You can see most of the other colors came up fine.
PS now you see why we don't buy expensive furniture :D