Hate to revive an old thread but...
Scalecoat SRR green is a little too dark to paint a Ps4 with. The real engines were actually 2 different colors of green and some of the engines were originally delivered in black paint. Early engines were Virginia green with gold leaf lettering which was apparently darker than they were painted later with a more yellowish looking lettering. Diesels were painted Sylvan green. There are a few color photos of the later green engines around, and they just look like a little lighter Scalecoat SRR green. Maybe the SRR Green is a match for the Virginia green, I don't know. I don't know that anyone alive now really knows what Virginia green looked like. Here are some color shots but none of them have good lighting. Also remember that the roofs of anything but a couple of the 6000 series should be painted black or green.
http://southern.railfan.net/im...n/steam/462/462.html