VGFacts

As we know, Dr. Eggman's nose normally is bulbous pink.

This however is not the case in Sonic Rivals 2.

For further examination, here's an Evolution of Dr. Eggman Video, along with all the Cutscenes in Sonic Rivals 2:

https://youtu.be/fGDojEyA9dc?t=11m2s

Just pointing out that the Old Egg Man has the pink nose for approval reasons.