Alain, what tools did you use to remove the blue cast? Just a "curves" adjustment?
Yes, curves. Essentially, I color balanced the image so that it has a neutral grey point. The original version did not. The area in the image used for the neutral curves adjustment doesn't have to be middle grey. It can be black or white or any value of grey as long as it is intended to be a neutral color.
I may also have adjusted the black and white points. I don't remember exactly. Once you have all 3 points set properly, you have a solid base to start working towards a master file.