If you're doing this in photoshop with layers, tryin knocking the opacity down on the color layer to make it blend more. Also, I do tons of track photography and I have never been a fan of that technique with race bikes...for some reason the color in the background adds something for me. PM me if you want a link to my track photos. Oh yea, and excellent shots!
I love selective coloring! Its especially cool for Prom/Winter Formal pictures. What I (and many others) do with them is make it all black and white except the girl's dress and the guy's vest and bowtie. I have some pretty cool pictures like that, if I think of it later I will put some up.
I like the first one, but it looks like somthing you would find on an inspirational poster - something like, "It's always best to be yourself!" or "Be original!"
I would just leave it black and white. IMO it seems a little cheesey.