Yes, the typical 'supermarket' variety of phalaenopsis can revert to dark pink/purple. I've never bought a purple one but I currently have three of them (marked on the pots as yellow or white/yellow - the colour they were when purchased)

Drat. I have another one which is the same colour and I was hoping for something different. I have never bought one, just either inherited or been given them, not my choice as I don't like indoor plants. Thanks for your reply.

It doesn't always happen. I'm sure there are plenty of people who get them coming back the same colour. Mine may have reverted because they were kept for 3 years in the wrong conditions - at my mother's we had them in a south facing double glazed porch. then they lived for a long time in my dark office (where the temperature was liable to all sorts of fluctuations). they survived (lots of healthy leaves) but they didn't re-flower during that time. Now they're in my kitchen - the ones that come into bud are moved to a south-west-facing window sill, the others are out of direct sunlight. I have a big, East facing window but I think that room might be too drafty (100 year old windows)