I was wrong - my mother noticed the weave. It was a pleasure to have my parents here for the Mother's Day weekend, especially after all the health problems Mum had in the winter. Dad had something he had to do on Friday after they got here, so Mum came upstairs with me and sat in my sewing room, reading, while I cut the fabric out. She would find amusing passages from her book and read them aloud to me while I hunched over the cutting table. It was most companionable.
As I was cutting, I asked Mum about which side of the twill she thought was the "right" side and she thought the more visible weave with the diagonal markings was the right side and after we talked about it, I agreed.
After I had cut out all the green pieces, I sorted out which pieces I needed to cut the underside in blue and pinned them to the blue twill and cut them out, leaving a half inch seam allowance on the collar, cuffs and bottom bands. Then I cut out the corresponding pieces in interfacing and arranged them all so I could make sure I hadn't missed anything.
Finally, I sewed together the blue and green pieces, using an old leftover green thread for the bobbin and the blue thread for the top.