Sewing strip with 2 different colors

hello I am sewing strips for an Afghan together and I don’t know what the best way is to sew them being that each side is a different color. one side of light gray and the other is black in stockinette stitch so I don’t know what the best way is to sew them together. Can someone help me?

I think it comes down to what you think looks best and what look you want.

I expect mattress stitch done in either color would look just fine. If you can’t hide the seams to your satisfaction then make them a design feature. You might consider picking up stitches on adjoining edges and doing a 3 needle bind off. Crocheting to join the pieces can give a nice result. I’d suggest a search to find examples or videos of different ways of joining the pieces together and seeing what looks best to you.

You could join with one of the colors or you could decide on a contrasting color (I’m so partial to red with neutrals) to add in something extra. There are baseball seams or the crocheted seams that GG mentioned that will let the seam color show.