How about Bali Blenders? I just looked up quilt fabrics and saw how pretty they are and they progress in color as well as texture - mottle. Yellow as the center would be pretty. As another mentioned, brown is the only other color I can think of that would go with the tan, teal, yellow and orange. Although, if you used teal as the center, I'd use that as the boarder too. I'm not sure what the cornerstones would look like - can't picture that, so I'm no help there
Perhaps a different shade of teal? That way, the quilt would seem like Fall with a bit of water around the edges.