Animation disappears after getComponent?

I have a little animation where a cloud of smoke explodes (2D sprite sheet) after its done u are left with a big grey cloud which fills the screen (this is supposed to happen) then i want it to fade away using color.alpha which i know how to do, but when all i do is imput this line:

 GetComponent<Renderer>().material.color = color;

The sprite just instantly dissapears when its finished its animation, how and why does this happen because i really have no clue and i need that to change the alpha :/ any help would be greatly appreciated.