I could not find a quick answer, so I ask, is the white on the 90-91 integra same as the 92-93 white? I know the 90 is called " polar white " and the 92 is " arctic white ", but are they ACTUALLY different? Or just different names? They look the same in pictures. I ask because I have a 90 GS and might buy some white body parts (hood, bumper, hatch) off a 92 white integra LS and hope to just install them with no painting required…
It’s going to be a different shade of white
When I get home, I can give you my 93 paint code.
I thought that 91 was Frost White just like the 92-93 (NH-538) and that 1990 was the only year Polar white was available…which is why if you see a polar white hood with an acura emblem, you know it is not a factory original hood…
Well, anyway, you can tell the difference and they are Actually different. I have a friend with a Polar White CRX and a different friend who had a 1991 Frost White CRX. You could tell the difference with them next to each other. Frost white is a warmer color if memory serves (although it has been a few years).
But I would say that if you have body damage or rust, then a slightly different white will look better anyway and you can always paint it later. Hell, get both bumpers and then it will look like you did it on purpose. 
Also:
http://forums.g2ic.com/showthread.php?80934-Paint-codes
http://forums.g2ic.com/showthread.php?114384-OEM-Paint-Codes-List
http://forums.g2ic.com/showthread.php?116347-Paint-Info-for-your-year
The last one is the most helpful as it actually has the PPG paint chips.