I hope the guys with more experience can help out with a bit of advice regarding hardener properties, or any chemist around ?

I got the hardener in a plastic container and realized that the cap cracked from overtightning. I probably realized this too late, fixed the cap but the hardener turned somewhat redish, darker colour.

Question - what does this to the chemical properties ? It probably reacted with air - but in a half full airtight container there is still air right, but does not necessarily turn darker.

The hardener seems to work the same way (subjective opinion- don't know if the mechanical properties actually changed).

Supplier has no idea about this.

Opinions ? Is it safe to use it ?

Regards,