Perhaps because I secretly miss the rigors of design school drafting classes, I used the excuse of the upcoming repairs and house painting project to draft up a plan of our condo and create a paint schedule. Because I'll be using four different colors for the walls--and some walls aren't going to be painted at all--I wanted to make it easy for the contractor to know what to paint where.
While I enjoyed the excuse to use my drafting table and parallel rule, making a sketch of your place needn't be elaborate; a simple line drawing will do. Indicate which paints go where with arrows, and create a simple symbol, such as a circle with a letter or number in it--for each color. Having such a floor plan, as well as written directions, is enormously useful to anyone helping you out.
There is, of course, the down-and-dirty Post-it method, by which you scribble out the color or an abbreviation on a Post-it and slap it to the wall. Just make sure you stick around to answer any questions in the (almost certain) event the Post-its fall.