I think making a Log Cabin quilt with just 2 colors would be very pretty if you used different shades of the 2 colors, not just each of the 2 colors exactly the same--ie. using blues in hues from light to medium or medium to dark or light to medium to dark. I agree with gayle bong that using the exact same fabric for all the logs would be a lot of work for what would basically end up looking like half-square triangles.