Not sure how many replies you'll get, so I'll mention that my wife does watercolors on many of our hikes. She's refined her kit over a couple of decades. She'll buy a few large sheets of high class watercolor paper and cut them into much smaller sheets, then have them spiral bound at a local Kinko's copy store to use for her plein air sketches. She uses a Windsor & Newton travel kit on hikes and refills the pans with her preferred color palette. She has a small travel brush she likes. It's all very compact and probably around a pound.

Often she'll do a quick painting in about 45 to 60 min after lunch. I don't mind the extra time to digest and read or write and it makes her happy. It's a regular part of our hikes together now.