My wife and i were driving to las vegas on highway 93 between chloride and dolan springs, az. to my left, at about 30 degrees above the road bed, and about one mile out i saw what i thought was two flocks of white pelicans. one group of about 30 and the other group about 20. i thought this unusual as i had never seen them this far south and inland. i pointed them out to my wife but she said she could see nothing. to me they were very obvious, how could she not see them. after frantically pointing to them for about twenty seconds they, all at the same time, turned a very light gray color. i thought they had all turned at the same time whereas the light was reflecting differently. i thought this odd as i had never seen a flock change at the same time before this. after a few seconds they all turned bright white again. i tried to point them out to my wife again but she said she still didn't see them. they turned light gray once more then back to white. i was coming up on a semi truck, so had to watch the road for a few moments. when i looked back to where i thought they should be, they were gone. i looked up and down the road way but saw nothing. i asked my wife if she had seen anything and she said she had seen nothing but dead bugs on the windshield but nothing at all that was white. she did point out that i was wearing sunglasses. i was wearing polarized sunglasses.