From Nita Leland's blog
Make a mini-watercolor travel palette
I can't remember now what got me started on this project, but I promised to pass on what I learned, so here it is. I used an Altoid mints metal container (2 1/4" x 3 5/8") and empty plastic half-pan paint wells. I glued the pans into the box using a hot-glue gun, which was less than $5.00 at WalMart (plus a bit for the glue sticks). I filled the wells with tube colors in a basic palette. You could set up different palettes for a variety of subjects and have a whole array of tiny travel palettes. The brushes in the photo were in the children's craft section and are a cut above most craft brushes. You could also trim off the handles of old watercolor brushes for packability. The whole kit--palette, an extra Altoid box for water, a brush and watercolor postcards, fits in a plastic sandwich bag.-- http://nitaleland.blogspot.com/2006/11/make-mini-watercolor-travel-palette.html
This idea totally rocks if you like to squeeze certain color combinations into discreet palettes. (I do) Go Nita, Mille Grazie!