Forging ahead with the blue fabric, I have finished the incredibly easy four panel skirt.
It will go with everything, including of course, the green jacket.
Except for the bands (cuffs and bottom) here are the contrast pieces. I tried doing the topstitching in blue on both top and bobbin threads to see how it would look. I used the tabs as test pieces because they are small and you never really see the undersides of them. I didn't like the way it looked (as I suspected) and so I did the rest of the contrast topstitching with blue on the top and white on the bobbin.
I also did the buttonholes on the flaps and tabs before sewing them to the jacket. I often do this because it's just easier to put them under the buttonholer but couldn't do it with the green jacket because I had not got the buttons yet. In this photo, you can also see the way the topstitching looks on both sides.
I am including this photo of the inside of the back yoke because of how I like to press things really flat. Even though the seam allowances get pressed up, I first press them open and then press them up. One more step but I think it makes the finish worthwhile. I tried taking a photo of the right side with one half only pressed up and the other double pressed but you couldn't see the difference in the photo. Of course, I can tell the difference in real life! Truly. :)
Here is the blue jacket on Rose, about half done, with one pocket flap artfully pinned up to show the contrast.