From a population of red, brown, orange, yellow, and green butterflies, only the red and green ones survive since they can blend into their environment and reduce predation. which evolutionary mechanism is involved?

The type of evolutionary mechanism that has been described in the statement in question is Directional selection. It is actually a kind of natural selection. It is the preference of one phenotype over another extreme. I hope that this is the answer you were looking for and it has come to your help.