The turret on the M113A1/FSV in the 1st pic. is off a Saracen, these were later replaced by Scorpion turrets.
The red plastic was for the .30 brownings, there was also a red .50 blank, black was 7.62, white for 5.56 and 9mm.
The Caddilac gauge turrets were in two configurations, twin .30's and the .30/.50 combination, later a Mag58 was added as a flex.