Turn on light

I have this button that is in black and white (grey scale) and I am trying to give it the effect like someone turned on a light so it changes into color like someone turned on a light.

Any one know how to do this effect?

Thanks…

In the “Over” state on your button, just add color to it, then when the viewer rolls their mouse over it, it will have color.

I think that is what you mean?