I have battern's flux in a clear plastic bottle with and the
fluorescent dye has faded it it, but the flux works fine.
I’ve had battern’s flux at my bench that didn’t seem to protect
gold from oxidation too well. When filling my small bench
container from the large bottle on the shelf I noticed crystals
growing at the bottom of the bottle. These were borax I guess. It
worked fine again after redisolving the crystals.
Personally I’ve never liked that neon green color, but there’s
no mistaking it for anything else.