I would agree on the airplane but when scanning a streep of green and your field of vision with 8by30 binos is 390 feet/1000 yards you will see contrast and difference. If somebody can't see a red bandana at 100 yard that that somebody shouldn't be conducting S&R. Take this pic for example:

http://brunerdog.tripod.com/contax/pages/upstate.htm

if somebody on the other side of that lake hanged a red bandana sqare and you were looking for him you would spot him right away. i will agree that during dusk or dawn your eyes will convert into more b&W vision in order to gain more light and than color will not make much difference but during day I don't see a reason why you wouldn't be spoted.