Clearly indicates what it says but not sure what the numbers, bars and colors mean. The manual mentions nothing on what these specifically indicate. Anyone knows?

I'd say it's the likelihood of hurting an enemy, depending on the distance. The colours on the chart are the same as you'd get when giving "fire" command. Therefore, if line of sight when issuing attack command was green, you have a 1/2 chance of hitting the enemy. If the line was yellow, the odds fall as low as to 1/8. Obviously, these functions are different whether you attack an infantry unit or a tank.