Trouble with Prefabs

I want to make different types of coins for my game (red, blue etc.) but even if I copy the coin to modify it and to make a new prefab, all the coins in the game change. I am quite new to Unity and I have been following tutorials on YouTube. Am I doing something wrong?

 

You need to create a new Material to do what you want. =)

http://docs.unity3d.com/Manual/Materials.html

 

Oh... Thank you Psyydack

 

You welcome, one more tip: you need create a new material and asign on your new prefab!