Alas, no Chris. As we have seen, actual colour images of these aircraft is very rare. I based the white wing tips on my 'Q' from a PTO Lightning (though it's were red with black trim) just on the basis that I thought it would look good in white with red trim and wasn't a stretch that an individual in the ETO might have done the same. It wasn't based on any prototypical 402nd aircraft in particular.
Regards your seeing the white wing tips in the images above, I'm not necessarily convinced though I can see why you believe they could be; they certainly appear lighter. However this could be down a number of factors. The increase taper of the wing profile allowing more ambient light to be reflected. I suspect that the wing tip skins are stamped/pressed structures to give them the shape - to accomplish this the metal could need to be a heavier alloy than the wing skins and grained differently. The forming itself could adjust the specular nature of the metal thanks to heat/energy transfer. Also bear in mind wing-tips tend to get knocks and bumps and maybe a newer (cleaner!) replacement had been fitted to one of these aircraft. Or indeed they may have been painted. A few too many equivocations to definitively conclude...