I prefer silver, or aluminum lettering on all my engines. However I have a couple that I purchased already painted, and they were lettered in white. The differences are pretty subtle, and not an issue for me. There is a color photo of #70 that clearly shows silver numbers on the cab.
Thanks, Tim. I think I’m used to seeing them in silver. I just got one in white, and something about it looked wrong, but I couldn’t put a finger on it. The tender need re-painting anyway (and I think it has the wrong road number to boot), so I’ll order up some in silver.
I have been involved either directly or indirectly, with restoration work on #60, #71, and #74 back in the 80's. Rick Steele carefully and meticulously removed paint exposing #71's lettering which showed positively that it was aluminum.
#60 and #74 were both Aluminum, although we found evidence of both white and silver RGS livery on #74.
I much prefer white decals on models and agree with Tim that the difference is pretty subtle. With the slightest weathering, you can hardly tell the difference. The reason I prefer white is that the silver lettering of the decals doesn't seem to have the correct feel, remember that this was aluminum leaf, or paint which matched aluminum leaf. Silver decals don't look like aluminum leaf to me. They just look silver, rather than the more gray appearance they seem to have been. #74's tender lettering was pretty visible indicating that it had been painted, but there was no sign at all that #60 was painted, but rather had used aluminum leaf only. That is the way I remember #71 as well, but Rick would know for sure.
I believe that the reason Thinfilm locomotive sets include both white and silver lettering is so that you can go either way. If you choose silver, they would certainly look better with a flat finish. I argued with myself back and forth over this in the 80's, and then I revisited that argument three years ago when I returned to modeling in C&S, and ended up with white lettering both times.
So either way you choose to go is probably OK. Sure is with me, anyway.