I started by scrap piecing remnants in that colour range.
Then I overlaid it with an enlarged transfer of a drawing by Ellsworth Kelly. This required a bit of puzzling around, with mirror image and transfer etc.
|not yet correct orientation of the overlay|
And hand-stitched over that.
Some machine echoing for the background.
Of course, I ran out of bobbin thread less than 10" from the end, but that's the way it goes. And I had just about enough thread left to put that on the bobbin to last me to the very end:
And this is the finished piece (minus the tunnel, which will follow in due time):
Now for the signs and symbols... yeah.