As long as none of the powder has crashed out of solution, you know the hormone is still intact. Good to Go!
Sometimes we coddle out gear a bit too much - steroids are very stable molecules. Even Gh and IGF-1 are more stable than commonly believed.
The "How and Why"
Trenbolone is more soluble in oil than in liquids like water, which is why we use oil, and not water, when we homebrew. Trenbolone also has three double bonds (D-bol has two, testosterone has one, DHT has none) that make it react with heat and light. When it reacts, oxygen is added to these double bonds, oil solubility decreases, and the hormone crashes out. So as long as the tren is still in solution, it's a safe bet to say the gear is still good.
The color change may be due to decomposition of BA or BB, bacteria in the gear, or spoilage of the oil (i.e. rancid).