setting and removing a tint

hi,
i have a button changing color onmouseover.
In some cases i want it to keep the same color, let's say black (even on mouse over).

so i use

acolor=new Color( mybutton );
acolor.setRGB( 0x000000 );

Now, how can i make it come back to the no-tint state (ie changing color on mouse over) ?
I tried

delete acolor;
or acolor= new Color();

But the button keeps it black tint.
Any idea ?

Thanks
Quentin

I think the only way is starting with a predefined color, and then use it again:

//first it is blue
acolor=new Color(myButton);
acolor.setRGB(0x0066cc);
//then black
acolor.setRGB(0x000000);
//blue again
acolor.setRGB(0x0066cc);