Erythrosine peaks at about 540 nm but depends on halide content giving slight shifts and changes in bandwidth. It depends on the yellow filter as to whether you can use one. Remember that Erythrosine is not recommended for Ag/Br/I emulsions by Mees, but old reports show it works well when added before precipitation. I suspect that the Ammonia is redissolving enough Silver halide to reform an Erythrosine-Silver salt or complex.

I've discussed this with Paul Gilman a while back and he is of the opinion that it has not been studied enough as it is such a poor dye in general. So, he had no real opinion on its use.

Best of luck.

PE