IMO, and seeing the pics you've posted she (Sandy) must have used the same colours for all the helmets. Why? THREE argues.
#1: She painted the three helmets with the same paint techniques, so surely the colours.
#2: As seen in the pic, she painted all the helmets at the same time so it makes no sense to be changing the paint in the airbrush to paint these if they were painted at the same time.
#3: I'm seeing in one of the pics FIVE bottles of paint: red, two greens, silver, and also the dark grey plus, IMO, the paint in the airbrush which is the one for the top of the cheeks. So SIX colours for those, just as they are.
The only colour I don't think that match the RotJ is the red for the mandibles, and it looks more like a red with a touch of brown, while the RotJ helmet, and IMO the Sandy helmet, has a red with a really soft touch of pink, more like a wine colour. Surely he used another red for the PP#2, as well as he used a light pink under the mandibles for it.
So, IMHO, any list would work, just the weathering will make the diference.