I'd definitely want an Amber Nymph against Rainbow. However, I agree that Purple Nymph is extremely useful: it practically insta-kills a creature, except it can still use its abilities.
I got an amber Nymph from the oracle, thats why i went crazy over gravity deck a while back, composed a 30deck card and tried for the FGs. My first akward moment starts from there~
Turns out that it went really well at the start, FG was rainbow, Mark was earth: i had it for PA and earthquake:
1st turn: all it summoned was one quantum tower, i had 5 gravity towers out with PA over it~ haleluya!!!!
2nd turn: it drew one card, then dispose of it again. My Nymph appeared on the battlefield~
3rd turn: it brings out an hour glass, i can already sense the sign of danger, Nymph baby suck sucky his quantums~~!!!
4th turn: Rainbow draws another hour glass followed by one quantum tower, I pull out an elite charger and kicks it over to my Nymph. Nymph sucky sucky quantum!!
5th turn: Rainbow draws another hour glass. I pull out another elite charger.
6th turn: Rapid explosion! rainbow draws 2 quantums towers, 2 supernovas, followed by 2 congeals my chargers, 1 thunderbolt Nymph. Ends turn by taking out one more hourglass.... i drew out another tower.....
After that it just kept summoning werewolves and forest spectres, too bad i didnt have a gravity shield back then, but the match went downhill and eventually he ended my suck sucky reign.
*think that was basically it, any other details i couldn't remember.... *sigh