Post a pic or two.

Most likely it's in bad potting soil. These plants grow in the crooks of trees, so their roots are well-adapted to growing in a loose, bark-based mix (much like Orchid Mix). In nature, they receive frequent rains, but the water flows through the bark and leaf-litter and the roots don't sit very long in the water. These plants are jungle cacti, not dry land cacti, so they must be watered much more often.

Purple coloration isn't a problem necessarily. Typically it indicates that the plant is receiving strong sun. But, in this case, it *could* be caused by drought-stress (not enough moisture, or dead roots). Again, pics required for a better assessment.

Josh

Thanks. I had no idea it was a jungle cacti. So I think I need to give it more water. It sits in a south western sunny window that gets a lot of sun. Do I need to move it to a shadier location? I think I need to re-pot it with different soil. I will try to post a photo. The thing is, now the leaves are droopy, not firm as they used to be.

Yes, water thoroughly and put it back in the window. It may take several days to re-hydrate. If you can easily slip the root-ball out of the pot, take a look at the roots to make sure they aren't all dead.

Josh

first and foremost, get it out of the median you have it planted in, and plant it in all orchid bark (they grow on trees in Rio De Janeiro, in the rain forest as they're epiphytes and not really cactuses) Also, during the spring and summer if you have them outside and it's hot, water every 3-4 days...but if they're just inside all the time water every 3 weeks...I've been growing these all my life, as my mom had them while I was growing up.

Silent - they really ARE cactus, just tropical, not arid land. Epiphytic yes, but still cactus.

silent, your photo is the way mine used to look only 6 months ago. Thanks for everyone's suggestions. So I will keep it where it is, in the sunny window and water more often.

The purple colour is said to be stress related from being kept in strong direct sunlight, so as they're jungle cacti they grow in shaded environments, dappled shade at best.

Gill