HI,
I hope that you repotted it into a pot that wasn't too large and with a light mix. The rule of thumb is to repot into a pot which is 1/3 the size of the crown. I always use a light mix of 1-1-1 peat, vermiculite and perlite. Your plant needs about 10-12 hours of indirect light a day to get it into blooming shape. If it all works out the leaf color should return.
Fred in NJ

My goodness...

I made about 8 post yesterday (1 to this thread)
and none of them are here :(

Dora

Red-backed leaves are fairly common--especially with Optimara plants which grow well in window light.

I think you will see the plant grow better as spring comes. If you have a good soil and give it fertilizer frequently, you should certainly see some changes in spring.

Fertilizer can be 20-20-20 or other, one-quarter teaspoon to a gallon water. Fertilize with each watering. Every month or so you might want to run warm water through the plant to take away fertilizer salts.

Nancy