My large Optimus came with BLACK stickers for the blue pieces. They're clearly black.

Some people are reporting getting correct blue ones, so keep an eye out, and try and make sure you do get the blue ones.

As for Prowl, you can make him look a lot better IMO by moving his wheels to his biceps, ala G1 etc. I also moved the lights higher on his arms.

Excuse the poor quality pic, I don't know where I've put my darn camera.

Here's what I mean: