Bonetto Cinturini 300D.
The strap colour works very well with this watch because it picks up the various whites of the dial and bezel. In other words, the strap is not a disjointed element distinctly different from the watch head (as would be the case with brown leather or most natos), but seems to be a visual continuation that is congruous with the watch head.
You could also use a black strap, but black is a non-colour. By definition, black absorbs all light. Matt black as a strap is like having no strap, leaving just the watch head as the object of interest. Originally, this padi edition comes with a navy blue strap, but it is so dark as to be almost black.
A red strap would echo the red portion of the bezel and the minute hand. I tried a red perlon strap and it's also a pretty good match. I imagine a blue strap that matches the blue of the bezel would also work.
The advantage of white is its sheer brightness. It's also an uncommon strap colour. It gives the watch a huge amount of sportiness and youth.
I'd like to try an orange strap with it some day.