I get out of old signs at work.
Your Engine Shed looks great. And yes, my LEDs are bright white. I did find I could have bought warm white (or maybe they weren’t offered when I bought mine - can’t imagine why I would buy bright white!) I ordered another string of ‘warm white’ for $3.17 incl tax and free shipping. I have used Testors auto brake/indicator light paint, which is a sorta translucent red or orange, to tone them down.
The LED packs are described as for signs - I imagine you put a transparent front over them. I found some in arrays of 4 LEDs or 3 or 2, like these. Here’s a test using a 9V battery toned down by Photoshop. In a real coach or building I probably wouldn’t be using more than 3 or 4 of the blocks. I ripped mine off the backing, but on inspection found I could have eased them off and retained the sticky foam and used it to mount them.