Transitioning 3 colors depending on int value.

Hello. I would like to implement this behaviour on my game: I have a green cube and I want it changing its color depending on the heat it has. Heat is an int variable that will have values between 0 and 200 (for example), and this is the color transition that I would like to achieve:

0-100: green becoming red.
100-200: red becoming black.

What I don’t know how to achieve is the effect of mixing colors taking into account the heat. I have tried using material alpha but the result is not what I am looking for, neither are lerps as I don’t want transitions in time.

Thank you very much.

public Gradient Gradient;
public Material Material;
public int MaxHeat = 200;

public void SetColor(int heat)
    Material.color = Gradient.Evaluate((float)heat / MaxHeat);