For me, it is waking up to realize that you can materialize your dreams. It is seeing yourself each day become what you have always wanted to be. Happiness is in being alive, living each moment, being yourself.
I'll borrow his idea of visibility of happiness though-> It's the total spectrum that matters. If you digitize it, you might find discrete packets which are not-so-happy, but the overall effect should be of the color of gaiety.
This reminds me of a poem I had read on a greeting card years ago, which keeps playing in my mind every time I make fragile efforts to define happiness:
Small joys and great ones too
Beauty to see and songs to hear
And wonderful things to do.
Enjoy each to the fullest;
For they add up to nothing less-
Than a life full of lovely moments
And a heart full of happiness."
What does happiness mean to you?