I"ve not done it,but they do it all the time on HGTV,decorating cents.Looks ok,as long as the other color is picked up and used somewhere else in the room,like pillows etc.
Kathi

You can do it, but you'll have to add some sort of trim, like a tassel or bullion fringe or bead trim (whatever you like). You didn't say if it's a solid or a print, but if it's a print, you'll need to match the pattern. Only problem with using the same fabric, it'll look like you had to sew two together. Using a different fabric will look like it was planned.

How about just a strip of another fabric between the two pieces of the same color? Then, Kathi's suggestion could be pillows of that fabric that the strip is made from. bggs

I think a beaded trim in between the 2 would also work nicely, or cutting the curtain into strips that run across, maybe 4 of them, then it would look planned.

Thanks everyone for your feedback. The panels are a solid color and my plan had been to use fringe or some sort of trim to disguise the seam, but maybe I should go ahead and add a coordinating fabric. By the way, the panels were 75% off and the perfect color, so I'm determined to use them!