What color plate?

That's kind of a hard one, Brenda. Hmmm.... I agree that the delete blank plate with the upper and lower does look a little off balance. How about a white background? It would pull the rocker panel color nicely to the front. However, I just chopped on the image above a white and then a black/grey one and I have to say - black looks pretty sweet!

Have you considered tinting the orange side markers? Perhaps with a 35% protective film. Then the black plate would flow real nice....
 
I vote for the background color to be the same as the car, with the lettering in bright blue.

I'm really glad I didn't need to make a decision such as this for my car. I went through enough angst deciding on license plate frames. I decided on no frame in back and matte black in front. I use the state mandated plates, front and back. Isn't it just great when the state solves some of your problems for you?