The following three links are the suppliers we use most frequently.  Thier sites offer information on the products they carry, color selection tips, and current color trends.

www.hirshfields.com 
 
www.sherwinwilliams.com

www.diamondvogel.com

Color Visualizers:

The Sherwin Williams website offers a color visualizer to help you choose a paint color by uploading a photo of your own home and "painting" it. 
http://www.sherwin-williams.com/do_it_yourself/paint_colors/visualizer/  

Diamond Vogel offers a similar color visualizer, it can be seen at:
http://www.diamondvogel.com/Architectural/Shared_Pages/colorvisualizer/colorvisualizer.html

Rochester area Realtors:

http://www.markkieffer.com/

http://www.gotoberg.com/

http://www.homeinrochester.com/