CTRLPalettes now color button text black or white for better contrast

app/js/ui/CTRLPalettes.js

 var Active_Color_Index = 0;
 
 
+function InvertRGB(hex){
+  var h = (255 - parseInt(hex, 16)).toString(16);
+  return (h.length < 2) ? "0" + h : h;
+}
+
+function InvertColor(chex, bw){
+  bw = (bw === true);
+  if (chex.indexOf("#") === 0){
+    chex = chex.slice(1);
+  }
+  if (chex.length === 3){
+    chex = chex[0] + chex[0] + chex[1] + chex[1] + chex[2] + chex[2];
+  }
+  if (chex.length !== 6){
+    throw new ValueError("Hex color expected to be 3 or 6 characters long.");
+  }
+  if (bw) {
+    var r = parseInt(chex.slice(0, 2), 16);
+    var g = parseInt(chex.slice(2, 4), 16);
+    var b = parseInt(chex.slice(4, 6), 16);
+    // http://stackoverflow.com/a/3943023/112731
+    return (r * 0.299 + g * 0.587 + b * 0.114) > 186
+      ? '#000000' : '#FFFFFF';
+    }
+  return "#" + InvertRGB(chex.slice(0, 2)) + InvertRGB(chex.slice(2, 4)) + InvertRGB(chex.slice(4, 6));
+}
+
 
 class CTRLPalettes{
   constructor(){
     var handle_syspalette_clicked = function(event){
       if (this.hasAttribute(ATTRIB_NESIDX)){
         var idx = parseInt(this.getAttribute(ATTRIB_NESIDX), 16);
-        if (idx >= 0 && idx < NESPalette.SystemColors.length){
+        if (idx >= 0 && idx < NESPalette.SystemColor.length){
           console.log(idx);
           // TODO: Set a selected Tile/Sprite palette index to the color index clicked.
         }
       var idx = parseInt(el.getAttribute(ATTRIB_NESIDX), 16);
       if (idx >= 0 && idx < NESPalette.SystemColor.length){
         el.style["background-color"] = NESPalette.SystemColor[idx];
+        el.style.color = InvertColor(NESPalette.SystemColor[idx], true);
         el.addEventListener("click", handle_syspalette_clicked);
       }
     });