This is one of my watercolor palettes, which contains transparent watercolor paints squeezed from tubes. It's the one I use when painting en plein air (outside in the air). Occasionally I like to experiment with opaque watercolors.
This is my gouache opaque watercolor palette, which I use to touch up plein air paintings if I've made a mess of them out on location, you know, when I want to cover up my mistakes to try and salvage a bad painting. It really doesn't work though, because it doesn't quite cover up! You know, watercolor takes a little more up front planning than oils or acrylics, and I just hate to throw those mistakes away without giving them a second chance. Another thing about watercolors is that they end up a little lighter after they are dry. You have to not be surprised when you lay in a nice rich color and it ends up looking a little faded when dry, and learn instead, to go richer than your eye sees, knowing it won't end up that way!
Recently I heard about casein watercolor paints. They are made with an ingredient found in milk. So I ordered a set and I've just started playing around with them. They are very opaque and they dry exactly as they look when wet. This is them, only 12 colors for now.
Here is a little experiment using a blue casein background and painting over it with two opaque white paints. You can see they both whites look like they cover pretty well when the paint is still wet. But when it dries...see how the casein in the second picture stays nice and white whereas the qouache looks a little transparent?
I hope you found this interesting and helpful!