During the One Year War, the Federation attempted to mass-produce the RX-78-2, but it was captured by Char Aznable. As a result, with little information available, they developed a mass-produced mobile suit that combined the artillery fire of the Guncannon with the close combat capabilities of the Gundam. This machine was deployed to the front lines as the RGM-79.
The RGM-79 was captured on the front lines at Jaburo, and given a Zeon color scheme by the Zeon forces before being dropped onto the battlefield.
The key point is that the color scheme has been repainted in Zeon colors. I thought that the light cannon would look good in a Zeon color scheme, so I painted it. Zeeg-Axe Gelgoog

Zeon Light Cannon | ミノきち's Gunpla works