Hi-viz "approved" colors
(Serious question - serious answers only please - at least initially. I know this question may invite ridicule at certain places. So feel free to start the ridicule, but only once a few serious and helpful answers have been given, and we're on page 2.)
Does anybody know if there's a list of "approved"/"recommended"/whatnot colors or designs for hi-viz vests, somewhere, for use at airfields?
(Reason I'm asking is we're organizing charity events at airfields where hi-viz is mandatory. We want the organizers to comply with the requirements to wear hi-viz, AND make the organizers stand out of the hi-viz wearing crowd for easy identification. So I guess the question really is: How do I make someone stand out in a crowd full of people wearing hi-viz clothing?)