Diff colors on gunsight

[SKYGUNS]

i was on the USS Jeremiah down in San Fransisco, It  battled in WWII on DDAY etc etc, although it no longer sees combat they still take it around the harbor.
It had 1 3inch, 1 5inch, and 8 20mm AA cannons. I sat in the gunners position on the 3 incher,  turned it left and right and elevated it up and down. looked down the iron sight then used the scope sight, i toyed with this nob on the scope sight and it had 3 different colored lenses not including the clear lense. it had red, yellow, and blue. Anyone know why?

[1pLUs44]

Maybe to see the planes/ships/targets from different angles at the sun.

[Tom5572]

The different colors bring out other shades, for example if you look through amber glass, red really jumps out.  We still use this today, though not for aa but for seeing wires and such when driving on the roads of Baghdad

[Maverick]

Some of it was to help view through haze as well.