How would i make an object change color every second?

Thanks for taking your time to answer this. I am basically making a game where you collect cubes with a controller. I would like the cubes to stand out, and i would like them to flash every second. By flash I mean change color. I have tried something like this: gameObject.renderer.material.color = Color.red; ...but that doesn't seem to work. Is this because i am using unity 4? (I cant use 5 as i work on this at school) I have also tried:`renderer.material.color = Color.red;` I have heard of lerp(), which smooths a change, but i will only use it if the flash doesn't work. I have looked at other question on this site and unity tutorial, but none seem to be any help...