Welcome to Photrio
@William quaintance ! I'm sure many here would love to read/hear/see more about your wet plate color process - including myself!
I have done some wet plate a few years ago, but ultimately moved away from it due to its practical limitations (the need to have a darkroom present at the moment/place of making an exposure). And the silver stains in my windowsills etc. became pretty bad, too...
I had pondered about extending sensitization, but never read about anyone extending it sufficiently into longer wavelengths to make credible green-sensitive plates, let alone red-sensitive. In your process, is color information recorded for blue, green and red, or are colors added at the printing stage?
I'd love to see that rose print in the National Gallery. I searched their collection, but nothing turns up that matches your description.