The properties of the molecules of air that make up the sky, mainly nitrogen and oxygen, tend to diffract the light from the sun more easily in the spectrum near where blue is. Thus blue light gets scattered around the sky giving it a blue color. This also explains why the sky can turn a reddish or pink color near dusk and dawn. The sun is low in the sky from your vantage point and has to go through more atmosphere to reach you. The more atmosphere it goes through the more of the red end of the spectrum it can pick up. That’s the reason it's easier to look directly at the sun during those times to. The bluish sky is also the reason mountains tend to have a more blue or purple tint far on the horizon because it is in fact similar to looking thought a very lightly tinted piece of glass.
What physical activity do you enjoy doing the most?