The stripes are on the fixed upper door skin and the lower door cover moves with the wheel and lower strut. Usually when you see photos the planes are at their lowest unloaded weight and most of the blue is visible because the struts are mostly extended. When the plane is fully fueled and armed, especially with a bomb or drop tank, the strut will compress and less of the blue is visible. If the compressed strut shows no blue and it in the yellow zone then it indicates caution, if yellow is covered and only red is visible then the plane MUST be serviced before flying. Some had only blue and red stripes for go/no go only.
The nipple at the top of the strut was for adding/relieving air to set the unloaded extension. There is a hydraulic fluid port lower on the strut. The struts were spring loaded and used ported baffles internally to slow the transfer of hydraulic fluid between the upper and lower chambers to dampen the bounce much like automotive shock absorbers on your car.
One of these planes is in need of service
