You might check with the Los Angeles Department of Cultural Affairs. They recently restored a 1930 movie house, the Warner Grand in San Pedro. In that project, they had someone who analysed and researched the old paint, and came up with original colors for restoration. After all that effort, they found a place where something had been bolted on to the building long ago, covering a place where all the original colors had been used. From that, they were able to check on their research.
Another thought on removing just one layer of paint would be to ask art restorers and archaeologists.