Hot pink! Only joking ! Brown is the usual color everybody chooses. If you can find a leather couch that comes in forest green, navy blue, or burgundy, any of those would be nice. If you don't like or can't find those colors, go with the dark brown and choose one wall to repaint as an accent wall. Use complementary, monochromatic, or analogous colors for the rug, accessories and pillows. Have fun!