I agree with Emma S., check out your closet and use colors you wear - they obviously make you happy, so why shouldn't you use them in your sewing room? My room is a medium purple with a few water colors (blue, green, etc.) thrown in for interest) - every time I go in there I am instantly cheered up. And if you can't find the exact shade you want in the paint store, take in some fabric or a piece of clothing in that color, they should be able to match it. Enjoy the process, and let your inner crayon-toting child have free rein!