อยากรู้ว่าเขาเขียน script ยังไงถึงทำให้ภาพเปลี่ยนสีครับ

<a href="home.php" onMouseOver="document.MyImage.src='images/enterOver.gif';" onMouseOut="document.MyImage.src='images/enter.gif';">
<img src="images/logo.png" width="219" height="229" alt="" />
</a>

<div align="center" class="bgTree" style="position: absolute; z-index: -1; width: 770px; margin: auto; top: 0pt;">
<img name="MyImage" src="http://www.theforestcondo.com/images/enter.gif"> 
</div>
<a onmouseout="document.MyImage.src='http://www.theforestcondo.com/images/enter.gif';" onmouseover="document.MyImage.src='http://www.theforestcondo.com/images/enterOver.gif';" href="home.php"><img height="229" width="219" alt="" src="http://www.theforestcondo.com/images/logo.png"></a>