If choose SCREENSPACE, the size in pixels will remain constant (it will look the same when you zoom). If choose WORLDSPACE, the size is in meters and will scale properly when zooming.
Configure the color of each axis (x,y,z) of the Manipulator. The 's' axis stands for the color when selected.
Visibility Behind object
Set YES if you want to keep seing the Manipulator even though is behind another object. Set NO otherwise.