I suspect that is Green-Yellow coloring, which indicates an Ammonia refrigerant leak (the color is the corrosion inhibitors), did you check for signs of leaks before you bought it? I ask because it may have been slowly leaking for some time before it completely failed.
Having said that 12-15 years seems to be about the average life expectancy for an RV refrigerator, some last much longer, and a few fail sooner, but somewhere around 15 years is about average life for an RV refrigerator or RV air conditioner.