Runway surface on Tinian Island

They would have looked like, well, crushed coral. Coral is a calciate compound and any that has been more than three days in the fierce tropical sunlight begins to bleach out. It eventually turns near white. Add to that the rain which is a conmmon occurence in the tropics and the motor oil would surely have begun to leach off.

I'd suggest that they would appear in scale as a lightly textured surface, tinted very light greyish tan.

I didn't have much time to research, but I'll be that there is some sort of after action report that details what color the fresh coral was.

 http://www.typhoonlarry.homestead.com/cb.html

Have you ever seen a sanddollar, fresh from the sea? It is sort of a greyish color with fuzzy stuff growing on it right?

Have you ever seen one after only a short time out of the water? They turn whitish grey within days and eventually near white. Corals are the same way.

The lovely, vivid colors you see in photos of undersea corals are correct - I used to dive in the FL Keys when I was stationed there in the Navy. However, give them only a short time out of the water and they turn dingy and soon whitish-grey.

Im certain they didnt use the coral fresh from the sea to pave Tinian, but rather something like excavated deposits. All in all, the color would be pretty much the same either way...greyish white.