It isn't the color of the hairs/pistils you should be looking at, it's the tiny trichs/crystals on the flowers which indicate when you should harvest. The pistils turn dark way before THC production has peaked.
Someone above mentioned a jeweler's loupe. You should try to get one online (they're cheap) and take a close inspection of the trichomes through it. When the little bobbles on the top of the trichs are mostly opaque, with a low proportion starting to turn amber, that's when THC production has peaked, and will begin to degrade over time. It's virtually impossible to see the bobbles without a loupe or macro camera; something with significant magnification.
Good luck.