After considering the three choices for top thread, I started with the darker variegated thread (right). It seemed to blend the best across both the light and dark fabrics. I began quilting with it and then decided to use the lighter (middle) thread. Sometimes you have to try quilting a bit to see which one works best.
I used a darker bobbin thread. When I use a 40 wt. as the top thread, I use a 50 wt. in the bobbin (always Presencia brand, my personal favorite--good for top thread quilting too!) There needs to be a slight adjustment in the tension so the bobbin thread doesn't pop up. Each of these three stitched lines were set at a different top tension setting--3.0 on the first line, 2.5 on the second, and 2.0 on the third. The 2.0 tension setting gave the best result for a balanced tension.
With the lighter thread (Superior's King Tut 40 wt. Color #904--Mirage), it blends right into the pink fabric. The original quilting plan was to quilt a grid out across the border. The grid looked a little lopsided and with the light thread on dark fabric it is difficult to hide the unevenness. A new quilting plan for the border will be decided later. For now there is plenty of stitching-in-the-ditch to be quilted in all the pieced seam lines, as shown above and below.
Starting at each corner of the quilt, I stitched-in-the-ditch across the bottom of the square, pivoted at the inner border and stitched down to the edge on the opposite side, pivoted and stitched back to the starting point. I did this on all four corners. Since the quilt is longer than it is wide, these "anchoring lines" created two large X's on the back of the quilt as shown here:
Always begin quilting with these anchoring lines so you can check the back of the quilt. If there are any puckers, you can fix them before moving on with the rest of the quilting.