Tell them with colour

Window sign at Zennkai Salon, Vancouver, BC

Colour is one of the most popular signaling methods for retailers. In North America red almost always indicates that there is a sale going on.

But what about bright? Is there some objective measure of "brightness"? Well there is for photocopy paper, but it is an indicator of the "whiteness" of the paper. I would assume that in this case the "brightness" is how fluorescent the sticker is. So, the more the sticker resembles a "hi-viz" safety vest the better the price.