do you mean roiboos or pu-erh "red tea"?
roiboos is a s. african bush without any caffeine, but with many minerals. i've not seen too much info on it but it's supposed to be very good for nursing moms + it has the bonus of tasting a bit like black tea (if you get those sort of cravings). yummy.
chinese red tea, like pu-erh, is still a variety of the "tea" plant, and has some caffeine though not as much as green or black teas - due to a different fermenting process. i don't know much relating to this red tea and nursing, but in chinese culture i've been told it's fairly cleansing and especially good for hangovers and too indulgent eating.
probably in moderation they are all just fine - does the water decaffeinating process affect antioxident levels in green teas?
(too bad decaf teas never taste as good)