The facination with colors

Tortoises I have found love certain colors and if an object is one of those colors, they love to bite at it. Orange, green and yellow are their big favorites. Not just a certain breed loves to do this but all of them love to. I feel that this is because these colors usually correspond to the colors of food they eat.
Here is an example.

While I do not know for sure that this is the reason why they love to bite certain colors, it makes sense to me.