I've never thrown any other swimbait than a Storm Swim Shad.  I have found that the baits produce well but I don't care for the colors they offer and sometimes the action on the baits are poor.  

I was looking at some L.A. Sliders and they looked like they would be a great lure!

My question is what size should I get and also what color pattern would be the most effective?

I live in Northern Illinois and the bass around here are not huge, but there is the occasional 3-5 pounder.  The lakes I fish are pretty clear and some get down to 25 ft. deep.  I know in California Trout patterns are good because they stock the lakes out there with trout.  The bass in my area have never seen a trout.  They feed mainly on bluegills, perch, and also some shad and crayfish.

The slider is a great bait, and a cheap one too. Megabiat stpped making them a couple years ago, but they just came out with the " Bass Grande" which is the same as a slider, minus the removable jig head.

The slider is best used in deep water, slow rolling on the bottom, I would recomend the 6" size. Whatever color you tyhink will work best, I think color is not that big of deal.