The green of the seamaster is darker in color, looks almost black in some lighting conditions. Green rubber works great, black rubber might be another option. If you think about the color wheel with green being a cross between a primary and secondary color, it might help with finding a good nato strap color. Dark green, dark brown, black, deep navy could all work. The other way to go is really light with the nato color for summer with white, tan, or yellow being good options.
Really depends on what look your going for, but a nato is a great option.