Define a JS method for mouseover and mouseout. In those methods, reset the source.
Ex:
<img src="images/--col---fix-12.png" id="img2" onmouseover="SecondImage();" onmouseout="OriginalImage();">
function SecondImage()
{
document.getElementById('img2').src = 'images/1234.png';
}
function OriginalImage()
{
document.getElementById('img2').src = 'images/--col---fix-12.png';
}