Scott,
The first thing to have in mind for the back and white of those times (that were developed with a gold treatment) is that yellow and red photographed as almost black. As well as other dark colours, which makes the process confusing.
I first check the newspapers of the date. Many journalists describe the first bunch of elephants with some colour reference, quite poor really, but something you can base on.
Then, I look for state references, like the colour of their flag or coat of arms, so I can check if the elephant is wearing a similar pattern.
For this particular elephant I had two colour references from the period: a Menpes plate, and a coloured glass slide.
I must say that, in my opinion, Menpes tended to colour the plates with the colours that he had at hand, and not the real ones. You can see that everything is yellow and red in this painting. The glass slide colouring is absolutely random. So these turned to be a reference that I had to decide if I should trust or not. Not having any other choices, I went for a yes.
The maharajas choice was easier. The source images are quite a reference:
This image was taken the day of the Durbar
In the cases I don't have any plate or painting to use as source, I use intuition and common sense combined with state colours. That has worked fine so far
Ana