The blending of an organism in an environment is best described by the term Camouflage.
Camouflage refers to adaptations that allow an organism to blend in with its surroundings, making it harder for predators to see them or for prey to detect them.
Mimicry is a different phenomenon where one organism imitates the appearance or behavior of another species, often for protection or advantage.
Natural selection is the process through which certain traits become more common in a population due to those traits contributing to improved survival and reproduction.
Evolution is the broader process of change in the inherited characteristics of biological populations over successive generations.
So, the correct answer to your question regarding blending into the environment is Camouflage.