SHouldn't the 2001 pattern be a lighter shade of green like it was in Jurassic Park III? Follow up question: Why aren't the 1997 T-Rex skin patterns labeled as MALE and FEMALE respectively like the 1997 and 2001 Velociraptor skin patterns are?
The JPIII rex isn't actually lighter on screen. People just think that because of an image they source it by, which isn't 100% accurate due to the lighting filter it has
(even the spino picture from the same source as the "light green rex" has the same consequence) that you may find online.
The beige skin was made so that it wouldn't be too similar to one of the already existing 1997 skins, let alone what the father rex in The Lost World film was like and attributed as in a basic sense. A
green t.rex. You know, they probably didn't need to add a 2001 skin due to similarities, but they still wanted to add them somehow. Further reasons I feel are too complicated to explain, plus I don't know all the details. But, I can say that
beige in particular was the chosen color because, according to big YouTuber,
TheGamingBeaver, who went to play an early alpha/beta build of the DLC from Frontier's early access event, he said in a video of his about after he attended the event, when he asked why it was that color, Frontier's response was that the JPIII rex animatronic
(which was actually the repurposed and fixed up father rex animatronic from the previous movie) was actually
more beige. It just depended on the lighting it was in because it still had a lot of green in it.
As for the male and female names, I think that was done to make all the JP rex skins cohesively grouped together by name, especially since there are alternatives for the 1993 and 2001 skins. Something the
Velociraptor isn't really like in a very complex manner. The dinos with A,B,C, etc. variants are basically the very same model and design patterns as the primary label, just with different colors. The rex has only one model and one pattern design from the DLC, even for all three skin eras, and all the extra 5 are just recolors as what some dinos in-game are like. The A, B, C, etc. are made as if they have 5 extra gene skin options as all dinos do in the rest of the game.
Velociraptor is way more complicated, so it's an exception, but the rex is a little easier to explain.