A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scattered out and away from the line of sight.
The volume of every sphere is
Volume = (4/3) (pi) (radius)³
When you say "across", I think you mean the diameter of the ball.
The radius is half of the diameter = 12 inches.
Volume = (4/3) (pi) (12 inches)³
= (4/3) (pi) (1,728 cubic inches)
= 7,238.2 cubic inches . (rounded)