When we get old why do our hair turn gray...irrespective of the original colour? Is there a message in it?

Yes....we are all mortal. That should be reason enough for mutual respect. But, as a human, I get to indulge in my own prejudices and biases depending on how I feel that day. We don't need to be different skin colors...except that it's a story of ancestry and environment; a testament to our history, for good or bad.