Red light has a longer wavelength (around 700 nm) and so is more affected by diffration than blue light (around 460 nm). Theoretically you could get about 50% more resolution if you used only blue light, and optimised the pinhole for the diffraction of blue light. In practise, I doubt it would be worthwhile.
Originally Posted by gattu marrudu
The size of the pin-hole determines the angle at which the light will diverge due to diffraction. The smaller the pinhole, the greater the angle. However when your FOV is 10 degrees, then a 0.1 degree divergence represents 1% of your FOV. The same pinhole on a 50 degree FOV camera would still cause the light to diverge by 0.1 degree, but now it's only 0.2% of your FOV. This is why diffraction is more of a problem with a narrow FOV. So, as you put it, the optimum pinhole is less optimal on a narrow FOV than on a wide FOV camera.