Astickleback fish will attack a fish model as long as the model has red coloring. what animal behavior idea is manifested by this observation?

Sign stimulus

Explanation:

Sign stimulus is a stimulus that will always produce the same behavioral response of an organism. In this case, red coloring is a sign stimulus for the fish attack which is its behavioral response.

This type of innate behavior is called  Fixed Action Pattern (FAP) because it is always the same (there is usually no variants in the behavioral response actions). If the model is colored differently, there is no behavioral response (attack).