About backdrops and a lesson in colour theory

Recently, Tony Thompson blogged about simple skyline backdrops.
https://modelingthesp.blogspot.ca/2018/05/about-skylines-on-backdrops.html
I was struck at how nicely his thinking dovetailed with mine regarding backdrops.
While I admire the talents and skills some put into highly detailed backdrops, I do not subscribe to that approach. Backdrops should be there to "frame" the layout, not upstage it. Backdrops should not draw the viewers attention away from the stars of the show, the trains and the supporting cast of scenery and structures.
Further along in his posting there was a photo of Brian Moore's layout over in Plymouth, England;

I was immediately taken with the colour choices  made on the sky and hill profile.
I shared this image with a friend who used to work as a Scenic Artist in the film industry, who pointed out to me that part of the success of the colour choices in this image is that they are in the same tonal range.
That is, go to the paint store and have a look at the paint chip cards that have 6-7 colours on one card. All of those 6-7 colours are in the same tonal range. My artist friend suggested I choose my colours off of the same card.
So I printed a copy of Brain's layout photo and trotted off to the paint store. Finding the sky colour was easy, but it took some time to find a card that had an acceptable sky colour and a nice hill colour but find one we did.

I selected a gallon of the colour shown on the left of the card and a gallon of the colour on the right end of the card, came home and practiced on a 3' section.

To say that I was pleased is an understatement.
Test bit done, I took a couple of evenings and did the entire backdrop behind Clovis.

There was just one more thing to do, I noticed, while in the paint store, that there was a haze effect in play on Brian's backdrop. A detail which really helped the overall appeal.
So I went back to the paint store and bought a quart of the next darker tone from the "sky" colour, thinned it and airbrushed a haze over the hills.

Just enough to slightly soften the edges and reduce the starkness.
I'm super pleased with the end result. And the backdrop colours, by accident, work nicely with the ground cover colours as well.
Glad I listened to my Scenic Artist friend!