Here is a 15 minute sequence of pics that shows how quickly the dye begins to breakdown.
1) Fresh sample Avgas in open glass jar, sunlight 30C.:
2) By the time I returned from bowser with 2nd sample (4 mins.), the first had turned purple (they are now side buy side, 2nd sample on right:
3) Five minutes later, the 1st sample has returned to blue (though cloudy) and the 2nd sample is now purple:
I have no pic of the last where both are green with parcipitate in the bottom and eventually all liquid completely evaporated. It goes pretty quickly.