Continuity mistake: While Riddick is being scanned by the Quasi-Deads, his anger causes the glass jars to break and the liquid to spill. At least seven distinct breaking sounds are heard. But during his escape, the glass jars are intact and there is no black liquid on the ground. (00:42:45 - 00:43:20)
Continuity mistake: When Riddick meets up with Jack/Kyra in Crematoria, she comes up behind Riddick and asks him if she should go for his sweet spot, Riddick grabs her wrist with his left hand and swings her into the bars. When she hits the bars he is holding her wrist with his right arm. Then a few seconds later you see his left arm again holding her wrist. With Riddick's left arm holding Kyra's wrist, his forearm is forcing her head to the side. This is made more obvious as Riddick then takes his right hand, grabs the bars and lifts Jack/Kyra up so she is now straddling his right arm. (00:51:05)
Continuity mistake: At the Crematoria mountain, Kira gets stuck in a small hole after the sunrise. She tries to climb again, but the rocks are so hot, she can't even touch them. She crouches and talks to Riddick for a while. Then, while standing up again, she touches the rock wall, but doesn't appear to experience any discomfort from the supposedly baking hot surface. (01:16:05)
Continuity mistake: Leading up to the battle in front of the hanger on Cremitoria we get a good shot of Riddick's curved knives in their harness with the handles up by his shoulders. When he finally draws the blades in battle he reaches back behind his waist to get them. (01:20:30)
Continuity mistake: In the scene near the end of the movie, where The Lord Marshall is choking Riddick, you can see that Riddick does not have his shiny eyes. You can see this when Riddick looks at the knife. (01:41:00)
Continuity mistake: The character Imam has a large animal tooth on a necklace. Later than 5 minutes and less than 25 minutes into the movie Riddick and Imam are having an argument where in different shots of the same scene two different necklaces switch back and forth. The first, which is a significant plot point later on, is longer and plainer then the embellished, more curved second one.
Continuity mistake: Jack/Kyra has a cleft chin in this film, whereas in Pitch Black she did not. Normally this wouldn't be a mistake simply because of recasting, but in the case of this film, footage is shown of Jack and the actress that originally portrayed her in Pitch Black.
Continuity mistake: When Riddick is with the Imam and remembers a previous event of saving young Jack from an alien, it shows a clip from the previous film, Pitch Black, in which we see him yell Jack's name before attacking the creature. He never did that in the film Pitch Black. It was added audio to show the viewers that he cared about her.
Chosen answer: The animals appear to be somewhere between a minor-class mimic of their surroundings and emotionally-triggered chameleons. As a sympathetic gesture towards Riddicks' dominant nature, it may have been altered purposely, or it was the animals' native eye color, when unstressed.