В HTML-низ.

Код:
<script type="text/javascript">
var color, href, time_color, rate=20, elmH=0, elmS=128, elmV=255;
function rotationColor(){
 if(elmS==0){elmR=elmV;elmG=elmV;elmB=elmV;}
 else {t1=elmV;t2=(255-elmS)*elmV/255;
  t3=elmH%60;t3=(t1-t2)*t3/60;
  if(elmH<60){elmR=t1;elmB=t2;elmG=t2+t3;}
  else if(elmH<120){elmG=t1;elmB=t2;elmR=t1-t3;}
  else if(elmH<180){elmG=t1;elmR=t2;elmB=t2+t3;}
  else if(elmH<240){elmB=t1;elmR=t2; elmG=t1-t3;}
  else if(elmH<300){elmB=t1;elmG=t2;elmR=t2+t3;}
  else if(elmH<360){elmR=t1;elmG=t2;elmB=t1-t3;}
  else {elmR=0;elmG=0;elmB=0;}}
 elmR = Math.floor(elmR);
 elmG = Math.floor(elmG);
 elmB = Math.floor(elmB);
 clrRGB='#'+elmR.toString(16)+elmG.toString(16)+elmB.toString(16);
 elmH=elmH+rate; if(elmH>=360) elmH=0;
 href.css({'color':clrRGB});
}
$('a').hover(function(){href=$(this); color=$(this).css('color'); time_color=setInterval ('rotationColor()',100)},function(){clearInterval(time_color); $(this).css({'color':color});});
</script>