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