current-color.js

(function(signal){
    
    signal({ 
      colors  : 9, 
      ttl     : 1000, 
      latency : 250 
    });

})(function(conf){

    var counters = storage.curry(conf.colors),
        history = storage(conf.ttl/conf.latency);
    
    var curr = counters(),
        next = counters(),
        prev = history.map(counters);

    function storage(size){
        return [].slice.apply( new Uint32Array(size) ); 
    }
    
    /// @exports:
    this.signal = function(color){
        return ++next[color] && curr;
    }

});

/// @usage:
console.log( 'signal response:', signal(1) );

/// @require:
Function.prototype.curry = function () {
  var fn = this, args = Array.prototype.slice.call(arguments);
  return function () {
      return fn.apply(this, args.concat(
          Array.prototype.slice.call(arguments)
          )
      );
  };
};