Factory two-tones were usually something like this pic. Where you draw the line is up to you but I just thought I'd give you a point of reference. Nixing the flames was a good idea on that style of truck. Some shades of silver/gray work well with dark blue. I would try to find some color chips and compare them to the blue you already have to make sure it works together. Good luck.
https://encrypted-tbn3.google.com/im...vxUtUi0LbgOgio