My first 2 Cockers were solids and my current 2 are partis and they've all had very charming, but very different personalities.
One of my solids was a cheeky, excitable and stubborn boy and the other was very gentle and eager to please.
One of my partis, William, is very laid back and confident. He's quiet and extremely affectionate at home and full of energy when we're out and about. The other one, puppy Louis, is on the go all the time (I'm sure partly because of his age) and very strong willed. At the moment he's the least cuddly Cocker I've owned, but maybe that will change as he matures.
I think colour has nothing to do with their personalities. My 2 solid boys were half brothers, nothing like each other, but both like their dads in personality. William is very much like his dad in both looks and personality and one of his litter brothers, who I see occasionally, is more like their mum in his personality.