I think navy or certain shades of purple could coordinate nicely if you want deeper colors, but a lot of green shades, with more warm undertones than cool, would be a versatile choice.

I am not a designer, though. My identification says "pro", but that is not our particular expertise. Hopefully some interior designers weigh in.

What color is your carpet, if you have carpet?
What colors are other pieces of upholstered furniture in the room or visible from the room?
What do you plan to purchase new other than the sectional? More upholstered pieces, window treatments, etc.?
Who, besides you, has to approve your color choices?
Wall color?
Any pieces of decor you have you don't want to part with?
What are the predominant clothing colors in your own closet?

The sectional is neutral. My first thought for an accent was purple or red. Some people would simply never want purple or red in their decor. That is where your own taste becomes important. What color do you like?

Yes, the color of other furniture and flooring is also important. What do you have? What is the wall color?