I thought I would chime in and refine bumpin's definitions as they are a bit off.

Redtop is called OptimaStarter it's designed to allow a car to sit for several months or more without being started and still crank without trouble. Redtop batteries are best for garaged cars, extreme cold weather, and cars that will be left on a charger often.

Yelowtop is called Optima Deep Cycle. It's designed to allow a SHALLOW cycle without a major loss in capacity. Don't mistake this for no harm. Cycling any battery will cause it damage, but the yellow top will not lose as much capacity. It also has a larger reserve capacity(about 120min) which allows you to run electrical equipment longer without the car running.

Bluetop Marine Cell batteries are a good blend of both worlds, they offer a very long storage time with a very low cycle capacity. They are designed to start boat engines and to run boat equipment when the motor isnt running. Generally you find marine batteries in groups to offer a very long operating time. larger work vehicles sometimes use marine cells to drive the wenches for towing.

All optima batteries are gel cell and charge faster and more efficiently than lead acid cells. In audio HQ, your best bet will be yellow top. I have a 78y Redtop because I dont drive when im at college and I have a conventional lead acid battery isolated for backup.