I know there is a post going, but the page would not let me add to the list – or read them all. Even if things are online you could have them do smaller home project with the instructions online. Probably everyone has some paper and color media at home. You could send some images as renderings that were painted and ask them to mix color for testing formulas in small patches and to try and simulate the color of something that was painted with a digital color tool.
Another option would be to have them begin a morgue of images for surfaces as Pinterest Boards or files and make the imagery be specific to a time, place, etc so they get that research angle going.
Third have them do some research – which can be online- on history of painting and color mixing. Not as lab oriented as a class, but keeps them busy and gives them some knowledge.