Answer: It might be just a case of immaturity. It isn't unusual for calla flowers to begin with a greenish tinge and then color fully as they mature. If they remain green without turning deep purple-pink by the time they're fully open, then I'd suspect the lighting isn't as intense as the plants require.
Wait and see what happens with the flowers. If they don't color up, you'll know to increase the amount of light they're receiving.
Q&A Library Searching Tips