That is an interesting question. I am sure this will get a few responses too as a number of people on here specialise on Giraffe.
I presume that the 'pure' Giraffe races in Zoos are all descended from groups which were initially imported from known sources in Africa and have bred 'pure' ever since. I don't know if DNA tests are available for Giraffe or are done in Zoos.? Or whether all reticulated Giraffe herds in Zoos nowdays are as pure as they should be.
If you look at another photo on this thread you can see this male compared to the young female 'Willow' that was born at the park last year.She is a much paler colour than this bull.
I would caution anyone against judging colour, in cases where the photo shows only one individual; there being so many variables which could affect this (eg. time of day, strength and direction of sunlight, position of subject, camera used, how the photographer processes the file, etc.). All of these would have come into play before I uploaded this photo
I dropped in for an hour today and tried to get a shot of all five giraffes together, in the same light, but that was a non-starter. I managed a shot of Bashu with Savannah and her daughter Willow, and hopefully that shot, and Chalklion's earlier shot of Bashu and Willow taken in softer light (and also suggested by Pertinax), give a better idea of the relative colours.
When I viewed all female adults and Bashu together today, I thought they were all of broadly similar colouration, although that was in direct sunlight and perhaps more difficult to judge. Eight-month old Willow does appear lighter in tone than the others, maybe because of her age?