function kleurknop(layer, kleur){
   if(document.getElementById){
      obj = document.getElementById( layer )
      obj.style.backgroundColor = kleur;
   } else if (document.all) {
      document.all[layer].style.backgroundColor = kleur;
   } else if (document.layers) {
      document[layer].backgroundColor = kleur;
   }
}
function lichtuit(layer){
   if(document.getElementById){
      obj = document.getElementById( layer )
      obj.style.backgroundColor = '#C2D3FC';
   } else if (document.all) {
      document.all[layer].style.backgroundColor = '#C2D3FC';
   } else if (document.layers) {
      document[layer].backgroundColor = '#C2D3FC';
   }
}
function lichtaan(layer){
   if(document.getElementById){
      obj = document.getElementById( layer )
      obj.style.backgroundColor = '#B3E6E6';
   } else if (document.all) {
      document.all[layer].style.backgroundColor = '#B3E6E6';
   } else if (document.layers) {
      document[layer].backgroundColor = '#B3E6E6';
   }
}