When you say orchid do you mean lilies!
if so dont worry its the cooler weather can do this, my lillies are poking through the soil and they have a mixture of green and some are purply.
A lovely flower, and the scent would knock you out.

One of my dendodrium leaves in winter leaves turned purple but have now turned back to green.

Think just the change in temps.

Thanks scotcat. I think your right the orchid is in the window and it has been very cold this winter, maybe the summer will cheer it up.