Quote Originally Posted by aged_sage View Post
...It must be remembered that the fish is looking up; directly 'into' the sun! Thus the bottom would either look whiteish (remember, the belly area of MOST fish is white for a reason)*, or have no 'color' at all. ...
...Frank
I do disagree with this observation, that in sunny conditions the bottom would look whiteish. The stronger the backlight ( the sun ), the darker the bottom of the fly should appear from below. In low light conditions ( morning, evening, cloud cover ), more color should be perceptible, and perhaps in optimum conditions, all color should be observable.

It is my impression that the underside of most fishies is "white" ( as an evolutionay response to their environment ) to disguise them from below, so that predators below them will not as likely detect their presence. Obviously in that situation both the oberver and the observed are below the surface and the light belly tends to blend with the lighter colors above the surface. Conversely, the top of most fishies seems to closely "match" the colors in the streambed the fishy inhabits. Again, that tends to disguise them from predators higher in the water column, or above the surface, like us anglers.

John