Super-easy Heatmap with jQuery

// This will look at all elements of class sel, check out their 'score' attributes, and set the background color accordingly (lightest = score 0, darkest = score 100)
// Individual element looks like this: <div class='sel otherClass' score=50'>Content</div>

$('.sel').css('background-color',function(){
   var how = $(this).attr('score');
   if(how>100 || how<0) how=100;
   how = how/2;
   how = 100-how;
   return "hsl("+180+","+50+"%,"+how+"%)";
});

// If you have separately-defined scale in a .css, eg:
//   .scale40{ background-color:hsl(180,50%,80%); }
//   .scale39{ background-color:hsl(180,50%,80.5%); }
// Then can use this:

$('.sel').addClass(function(){
   return 'scale'+$(this).attr('score');
});