i used superbrightleds products brightes i could get and never tried the rear, but sure is no difference from the front, i changed mine to yellow cause white isn't as much noticable during the daylight almost have a head on with oposite traffic
This can vary from state to state but I'm pretty sure every state requires that rear markers be either red or amber and front markers be amber only.
The real question is, if you change it will local LE even bother giving you a hard time? I've got tint on the front windows that's much darker than the legal limit and I've never gotten harassed. Even passed state inspection with it but stuff like that will only be a problem if you drive like an a$$ and attract attention to yourself.