Tossin' out some Berkley Powerbait is a very easy way to get started trout fishing--the stocked trout eat it up like crazy.
There are a ton of colors, sparkles, shapes, sizes, etc. (and that's just in the Berkley line!). The "dough" may be the original, but most people I see use the nuggets, dough, or salmon eggs. Personally, I prefer the newer Gulp! line of berkley products as they are 100% biodegradable.
Last summer I took out about 12 different types of Berkley powerbait to satisfy this very question and when the fish were biting (again, talking about the stocked ones here) they did not discriminate. Pink, green, yellow, sparkles, nuggets, eggs, dough--they ate it all up the same. Therefore, I prefer the "Berkley Gulp! Salmon Eggs" in pink or red. They stay on the hook a bit longer than the nuggets. If you can manage to set the hook before the fish swallows it entirely then you can keep on using that bait all day long. However, I usually have a jar of yellow or green Gulp! trout nuggets with me as well.
The scent--in my opinion--is probably the main factor here. Visibility a bit too. But since they are all the same scent, I would just pick your flavor and go nuts. Orange/Red/Pink are what I see most often. I'm sure people will swear by one or the other... and the one that got away.
Along the same lines... I see a lot of different rigs for trout fishing powerbait and I've tried a lot myself. I found a very simple rig is just as effective as the fancy ones (at least for me). Egg sinker, swivel, leader, single-egg hook. If you need to cut the hook off, you can just pop a new one on the leader and be back in the water in seconds. Using multiple hooks or any other fancy rigs tend to result in spending more time untangling or re-rigging than anything else (not to mention you use up your bait more quickly)--and when the stockers are biting you may be pulling 'em out faster than you can re-rig.
The one factor that *does* seem to matter is the length of the leader. The powerbait floats off the bottom. It's usually in the range of 12 - 36 inches for me.
Then once you catch enough for dinner, swap out that powerbait for a spinner or spoon and go for the bigger ones or catch n' release.