I think camouflage would be great! (Obviously. Check the username.
As mentioned already, camouflage could be utilized for:
• Color puzzles
• Temporary invulnerability to certain conditions
I think camouflage could also be useful for:
• Evading enemies
• Confusing prey and predators
• Shaped-based puzzles (e.g., lining the duo up against hieroglyphics)
• Time-based puzzles (Suppose that certain play tonics change Yooka to a certain color. Now suppose that there's a rainbow play tonic, with which Yooka's color cycles through various colors and you must place Yooka on certain surfaces at specific moments based on the timing of the color changes.)
I'm quite certain that I saw in one of the many videos or written interviews that camouflage will be one of the many character features, so I think we can can count on its presence. Even if you don't like these ideas presented in this post, remember that this game is being developed by a group of experienced genii. They'll come up with something good, for sure. Or maybe several somethings.
As for other character features, tongue grappling, sonar blast, and temporary flight have all been confirmed.
Yavga above mentioned chameleons being able to climb trees but not mirrors. Obviously some realism has to be broken (or rather, stretched) here, but I think Yooka being able to climb o