Purple dye is notoriously unstable--that is why it is harder to find purple fabric. Red is also risky. How many folks are wearing pink underwear & athletic socks right now? I pre-wash all fabric whether it was from the $1 table at Wal-Mart or $11 per yard at the LQS.
Definitely color test each & every batik. Some fabric that looks like a batik is really a print with an over dye. It will shrink a lot more than the true batik. True batiks are boiled to get the wax off so there's not much chance they will shrink but some dyes just don't "take". I love hand-dyes, tie-dyes & most batiks but mixing them with light colors without first testing them is a disaster waiting to happen. Oh, and test in both hot & cold water. I've had a few weird ones over the years that appeared to set in the hot water but when cold water was splashed on them after they were washed, dried & pressed--they ran a little bit.