when was antique brown bronze replaced by yellow bronze?

Answer 1

You need to expand on your question. What type of sculpture? The old stuff looks that way because it is old. We got all up on shiny brass for light fixtures and door knobs - then antique - now those items are becoming popular in pewter. Please add some details.

Answer 2

"Antique" brown bronze is just a surface treatment called patina. The same material can be polished to a bright yellow surface or be given the patina treatment to turn it various dark tones, which also protects it from further weathering - polished bronze has to be protected by laquer like polished brass. The same casting foundry can produce either - I was looking at a pair at the Nasher Sculpture Center in their current show "Woman: The Art of Gaston Lachaise"
Providing coloring by chemical patina application has been done at least since Roman times.