RCDs & M3 75mm GMC?

[Dave Block]

Hi all. There's a photo on Library and Archives Canada (PA201371) showing an M3 75mm GMC with the RCD in Italy, May 1944. Does anyone have any details of their service, i.e. how many, time frame, etc.? I found a thread on one site that suggested the GMCs were used until Dec. '44 when they "wore out".
Is it possible that they would just remove the 75mm & continue to use the halftrack as a GS vehicle? Spares shouldn't have been too much of a problem as the US was using the same basic halftrack as well.
As well as the name "FOX" on the vehicle, there is an 'A' squadron triangle on the side. Any idea as to what it's colour might be?

Many thanks, Dave