The light blue of the sky is the color associated with calmness and with healing. 

A dark blue sky signifies the coming of another night and
sometimes a storm. 

When our primitive ancestors looked upon the light blue of a new day, they felt safe after shuddering in the fear of the previous night of darkness and the dangers within it. 

People who are ill feel at ease when seeing each new light blue sky, and take comfort in knowing they've made it through another long night. 

Blue’s strongest association is with the sky and the sea. Although a cold and retractive color, blue is said to have a pacifying influence. 

Blue also symbolizes peace, faith, contemplation, truth, and heaven. 

Dark blue has long been associated with power and authority as attested to by the color of the uniforms of policeman - as well as other careers and professionals.  There are the military uniforms, the cape of an RN, and countless others. 

Blue has long been associated as the color for baby boys.

In heraldry, blue is used to indicate piety and sincerity.