Connecting Threads...in Quilting

When I am quilting an image which will include varying thread colors adjacent to each other, I will if the quilting plan permits, try to interlock one thread color into the adjacent thread color. That means whichever thread is quilted in first must be done so as to leave room for the next thread's interlocking quilt line. Here's the near edge of the rounded plane fuselage. It is darker on the side of the plane that is away from the light source.... so I've saved room for a darker blue thread

The opening left in between the lighter blue thread permits the darker thread to interlock and thus provides a more gradual pleasing value transition.