The Randomizer, an add-on for Illustrator, takes the objects and swatches you select and randomly applies the colors to their fill and/or stroke colors. Variable stroke width is a bonus option.
And then it can do something crazy. You can Batch Save up to 100 different variations as an Illustrator and/or PNG file. In the Export section, click on the Make Magic button, go watch a movie, and when you come back there should be tons of rendered color variation files ready for you to review.