Hairs changing colors has nothing to do with harvest time. Some strains the hairs start changing early. The hairs start changing around 3 weeks on the stuff I'm growing now- and it's not because of any problems. The plant will brown pistils and it will grow more during flowering. That's just how it goes- one day the pistils could be 50% browned and the next day a ton of new white ones grew. The only true way to check for harvest time is by the color of the trics. Get a microscope.
You shoulda seen me with it.. LOL... sit there for ten minutes, get a few fleeting glances... enough to where i think i know what i saw, but i need to verify.. LOL..haha.. you know thats right!! for the first 2 hours after i bought that thing i was about to take it back.. thought it was broken,,,, just takes a steady hand like u said ( and u have to take into consideration that the image is inverted so if u want to see more of the upper right of the image u have to move it down/left ) youll get the hang of it..