In its early days, the neon open sign has been rectangle with blue borders and red letters. The latest signs of this kind, however, have more prominent colors, with fuchsia, lime and many more available in the list, along with the tubes containing gas littered with ink. There are, of course, many more variations of the open sign, like the scissors in those barber shops and the ever-familiar neon beer sign in those pubs. So to speak, the open sign is actually the precursor to the huge burst of neon signs in cities and night shops.
Specifically, the start of this huge burst in popularity first started at the strip malls of immigrant business owners (like Earle Anthony), who obviously wanted to let people they were open for business. Again, the glowing signs attracted tons of attention, drawing human and vehicle traffic. Furthermore, it helped those companies that are conventionally closed at night to tell their customers that they were still open, like the coffee shop neon signs.
Competition began to take its toll and neon business signs began appearing everywhere, with creativity producing the neon haven that is Las Vegas. It's pretty funny and amazing how a little neon open sign created Vegas, right?