In Jurassic Park III, most of the dinosaurs that have been seen throughout the movie have made appearances in the previous movies such as the Brachiosaurus and the king of Jurassic Park, Tyrannosaurus Rex.
People had noticed the significant differences between the species of dinosaurs in the previous movies and this one.
Brachiosaurus
Parasaurolophus
2 dinosaurs for example, the Brachiosaurus and the Parasaurolophus, have significantly different colors between movies. In the last movie, the parsaurolophus would have a bright white underbelly and brown over the body with dark brown stripes. The brachiosaurus would have a brown based body with a slightly lighter opacity on the underbelly, however in jurassic park 3, they hae a light green based body with slightly darker green stripes running down it with a red crest on their head.
A possibility for this theory is that with each generation of each species proceeds, each generation changes pigmentation and other features. the Parasaurolophus has green pigmentation to better blend with the surroundings. Another possibility would be that it does not affect the species as a whole as the movie shows them being in a different part of the same island with The Lost World. Meaning it might depend on the surroundings of the creature to adapt throughout their generations. With such speed of change, assuming this is the case, would possibly be a side effect from genetically modifying and cloning them.
Here is how the Parasaurolophus and Brachiosaurus would look like form the other movies.
Brachiosaurus from the first Jurassic Park movie.
Parasaurolophus from The Lost World Jurassic Park
This also applies greatly to the Velociraptors from the 3 movies. This is also the first time in the trilogy that there is a physical difference between female and male raptors.
Raptor variant from Jurassic Park(1993)
The Lost World Jurassic Park(1997) Raptor variant.
Jurassic Park III raptor variants. Both Female(left) and
Male(right) velociraptors.
Credits to Jurassic Park Wiki - Wikia for additional information and images.
Credits to IMDb for information references.