Sounds like Automatic or vintage gearoil if not coolant.
" 
Automatic transmission fluid (
ATF) is a kind of 
transmission fluid used in vehicles with self-shifting or 
automatic transmissions. It is typically coloured red or green to distinguish it from 
motor oil and other fluids in the vehicle. "
	
	
		
			
				
			
			
				
				
				
					
						
							
						
					
					en.m.wikipedia.org
				
 
			 
		 
	 
" Green Gear Oil, GL1 (SAE 90, SAE 140), provides the lowest level of performance and is suitable for vintage transmissions. It is very similar to engine oil, having a very low additive content, but is available in much higher (thicker) viscosities to suit gearboxes with unsophisticated oil seals. "
	
	
		
			
				
			
			
				
				Green Gear Oil GL1 (SAE 90, SAE 140), provides the lowest level of performance and is suitable for vintage transmissions with yellow metals.
				
					
						
							
						
					
					www.millersoils.fr