If I look at for example my curtain I see that it is green. But why does it have this colour? I know it has something to do with all colours except the green being absorbed but the curtain is just a pile of molecules. So how come this pile has colours? and how come not all substances have(for example glass doesn't have a colour)? Paul P.S. could the person answering this please explain it in plain, easy english because I'm just 15 years old and I live in the Netherlands.