I carry the paints and media in a blue canvas folio. It holds my field drawing board, which has a appropriate sized nut glued on the underside so I can amount it on my camera tripod if a portable easel is required, but normally using it on my knee is fine. This board is just a bit larger than a quarter sheet of watercolour paper and I usually carry 4-8 sheets held in place for transport with rubber bands. I often have a sketch block or watercolour pad included, although I now like the idea of having a few post card sized pieces of watercolour paper as well. I sometimes finish a sketch, write a message on the back and post it (my post cards from Canada were popular with my family). I can also fit a full sized plastic palette and my canvas roll of my watercolour brushes. Its a pretty light setup and the canvas handles make this easy to carry. I usually also carry a full set of watercolour tubes in my luggage in a largish plastic screw top jar which can double as a water jar when needed, I seldom take these out sketching. The orange flagging tape is to make the kit easier to find in the field, whilst the blue is strong it can disappear when left in the shade, the orange tape against the blue is hard to miss.
I also still have my foldout studio always ready when I want to create a decent work place on the go. However this blue bag kit is what I will be taking in my luggage for most of my Endless Summer project trips.