Draw the animal faces on the appropriate colors (sorry these 2 pics are blurry!). You can also print these from free clipart online.
This is how I presented the activity to D (2 1/2 years old).
He did the gluing and here is what we ended up with:
Variation: Instead of using googly eyes, draw in some eyes and then Laminate bookmarks for durability.
What is your favorite size of bookmark?