I can't see much difference in color and I have a vial of test/eq blend and it's 9months old and a few weeks ago I noticed it had gotten darker-I'm gonna still use it but I'd say if yur second guessing I woupdnt chance it-pitch it but I think that in time the carrier oil darkens and also u can ask the source how long he has been using that carrier oil in his gear for that particular compound-for maybe he has changed the oil/process/brewer ya know?
Hope that helped and good luck