I've recently been involved in a yellow sticker incident involving neons, so I can quote first hand what is and isn't allowed.
The law according to a Dept of Transport vehicle inspector:
Neons are legal under the following conditions,
You must not be able to see the elements from a seated position in an ajacent vehicle, neons are not allowed to pulse or flash, you must not have a red neon facing forward, all other colors are acceptable, all colors including red are acceptable for the sides and rear, they must be adequatly secured and the elements shielded to avoid exposure to other drivers. You can drive around with them on.
The law according to some cops:
Yellow sticker every vehicle with neons as they are deemed a distraction to other drivers, you can't have them on whilst driving but static in a carpark is OK.
My personal suggestion is put em on the correct way, use them and know the law and your rights if you get pulled over, just remember though it could cause the cops to look for other defects on your car so keep it neat and legal.