I think your biggest problem will be finding buildings that look like cut stone. Most kits I’ve seen are either simulated brick, wood, or concrete. If you do find a suitable kit, then painting it the right color will be the only issue. I have a couple of things on my layout where I needed a limestone look. For both situations I used a flat tan paint, then a few washes of diluted acrylic paint. I think I used yellow ochre and raw sienna. The washes or ‘stains’ give the surface the mix of colors instead of a solid appearance.
I don’t have any limestone buildings, but here are a few shots of the places I needed that look. In person they don’t look quite as yellow as in the pictures.
I also like the “textured” spray paints. Rustoleum makes several different colors. This is a theater wall I sprayed with one of their “multicolored” textured paints:
They also have single-color paints that would be more applicable to a limestone look.
The thing that makes these paints work is the rough surface that’s left after the paint dries. It reflects light, or rather “scatters” light, much more realistically than a flat plastic surface or even one covered with flat paint.
The colour of your limestone will vary depending on the quarry from which it came. I don’t recall the Floquil colours used for my station, but a mix of Grey Primer, Depot Buff, Aged Concrete, and perhaps Reefer Yellow seemed to simulated the colour of the limestone used in this area. Construction is .060" sheet styrene, with the same material, cut in strips, as interior bracing. Doors and windows are modified leftovers from a couple of Walthers “Waterfront Warehouse” kits. The architectural details such as banding and cornices is strip styrene. I scribed the joint lines using a straightedge and a #11 blade - one pass with the blade, then a pass or two with the back edge of the same blade. Weathering is minimal, as this is meant to represent a fairly new structure, and the details are sparse, as it’s a background building. It still needs some signs to denote the Express wing, on the left, and the Post Office, on the right. There’ll also be a free-standing station name atop the canopy.
Jim, this is the new layout. The depot area is further along than this photo, but it’s the only shot I’ve taken so far. I’ve spent a lot more time on the trestle area then the rest of the layout. Needless to say, if this layout ever meets the trash heap, the trestle section will live on. For some reason it’s near and dear to my heart. Thanks for the compliment.
I think you will find the answer to your questions in the new issue, (February issue), of RMC. They have a short article on making cut stone as well as coloring it.