Etymotic ER4P - New & old versions? Differences?

Hi all,

I'm pretty much a newbie to all this. I'd like to get a decent set of earphones for my Ipod. I travel a lot so noise isolation is important. The Etymotic ER4P's look great to me but they're very expensive new. I might get a good 2nd hand pair and noticed that there are 2 versions out there. The older ones with blue & red sections to show left & right ears, and newer ones that are all black.
The all black ones look a bit better but is there any other difference?
Anything else I should know about them?

Thanks