mine is still variated or more variagated since i got it. However someone who studied plants, an agronomist explained to me that variagation is caused by a virus. I suppose your plant might be curing the virus somehow.

Oh, I think it's far more likely that as the leaves age and the light improves, they will show their variegation more clearly. Some among the same clones usually tend to be more variegated anyway.

Variegation is a chimeric mutation that can happen several different ways. It's not always stable and can revert back at any time. I suspect if the plant was not heavily variegated to begin with maybe it has more chance of reversion in new growth. You could always remove the non-variegated leaves to see if you can get some color in the new ones.

I noticed you have it in a gritty mix, do you fertilize when you water? If not, maybe this is causing a reversion?

-Erica

A common cause is not enough light, or for some succulents, too much sun.

I had a 'Red Horn' and it broke apart falling onto my deck. Resulting growth shows no variegation what so ever. Sorry, didn't take current picture yet.

Before;

Stush

Stush - 'Red Horn Tree' is not technically variegation, though I am not sure what causes it - It's similar to 'Hummel's Sunset'. It tends to turn green during the end of winter and through much of summer. Once the cooler, longer nights start in autumn the colors on the tips of the leaves become more prominent.

-Erica

Stus

transformation of the chloroplasts into the chromoplasts is the cause of these colors. This occurs under conditions when it is impossible the formation of chlorophylls. But it's enough light, water and traces of magnesium and iron. The chlorophylls can form at +10 - +30°C.

Oksana