Another alternative for those who feel "constrained" wearing tight painter's white pants: overalls. Never overlook the trusty painter's whites in overall form.
They are, by nature, much looser-fitting, and they somehow carry an air of authority - I have found that when wearing the overalls on a job, the clients seem to perceive me as the foreman - whether I am or not.
Just offering another alternative for those who are not comfortable wearing whites, as there seems to be quite a few of y'all...
EDIT: That "Centaur" brand of whites I mentioned in an earlier reply - here's a link to the manufacturer. The ones I like are the Model # PDDK (the first ones listed). The lower-grade version are just made out of canvas dropcloth material and very much feel like the Dickies or Stan Ray brand, but the heavier ones are so comfortable that I'd actually wear them on a day off if I had no other clean pants.
I buy 'em locally at one of my independently-owned paint distributors.
http://www.acedropcloth.com/clothing.htm