I am making a MouseOver function and its not working

Im making a slender game but i cant make me text light up when i pull my mouse over it, does anyone know what is wrong with this code?

var initialColor : Color;

function Start() { initialColor = renderer.material.color; }

function OnMouseOver() { renderer.material.color = Color.red; }

function OnMouseExit() { renderer.material.color = initialColor; }