As stated in TFA, the pictures were originally black and white and were colourised at the time. I cant find a record of who colourised them or when, but it sems to me like they were colourised shortly after by the original photographer, and as such the colours would be reasonably accurate. You can see lightness and texture changes that would imply to me that there were changes in the material at the time of the picture being taken, even if it was colourised incorrectly