Red = Starter batteryThe yellow top is deep cycle battery, the red top is for general automotive with cold cranking amps.
I use to run Optimas for years. After they sold to Johnson Controls in 2000 and started making then in Mexico, their quality went downhill and their warranty isn't as good anymore. Not worth the high cost for those batteries, IMO.
If you want a good AGM battery, I would look at the Sears Diehard Platinum. They are manufactured by Odessey and about the same price as Optima, except way more reliable.