I opted for white led's as I am getting a tad bored with yellow (or my eyes are getting worse?) Any way Patience being the most important attribute to modelling (just my opinion?) I played around with a few idea's and did not want wire, led's and resistors all hanging around like spaghetti so I used bread board, I believe that's what it's called, 20 thou plastic sheet with a 60 thou strip added to give it support I wanted a minimum of wiring showing when the roof is off, and I believe that was accomplished by 20 thou pretty much hiding over 90% of it all. The outside lamps are simple shaped and fed through and soldered to the bread board and a spot of super glue just for good measure.
When all is working a quick spray of matt black and that pretty much hides the wires to the outside lamps.
By the way they are running a 9 volts dc.
Because of the light and conduits I had to make some (on the job) modifications to the removable roof supports.
You can see the flues for the smoke.
Just so you can see the loco name .Wheldale.