I was going to mention the rubber label with the date of manufacture, but Dennis beat me to it. I started a 41 plus years in train service in 1960 and the labels
were on almost all air hoses. They seem to start disappearing in the mid 1960's. They were about an inch wide and three inches long, red was the only color I recall.
The only time I recall seeing glad hands that looks silver was when they were on new cars or had replaced an old hose. They were weathered a very dirty color.
The angle cocks were a gray color if unpainted, although many were painted the same color as the car they were on. Most air hoses had hose clamps at each end
to hold the glad hands and the threaded casting that screwed into the angle cock. They were often a stainless metal color.
A DRGW flatcar has a new hose showing the color of the glad hand when new.
The PFE reefer and GN boxcar shows the red label well and weathered glad hands.