R59 top post battery

[cruiserofland]

I turned my R59 topper into a Y55 (except for polarity) with a little Dupli-Color touchup paint plus a real Delco Eye I found online. Cut the bottom off the plastic site glass to be flush with the topper base, and painted the Delco Energizer lettering too, like an over-the-counter battery, since it looks so good like that. I used black tape to hide the top of the battery but I like the idea of green tape to mimic how the real eye worked. Was the green some sort of plastic indicator of battery health, or was the fluid in the battery itself just green? Showing my age here a bit as I've only ever had sealed batteries...