Hate to disagree but trich color IS how you tell when your plant is ready to harvest..

You should not see clear, you should see all milky and a percentage (based on your preference) of amber trichs..

Anything below 60x will not cut it for proper inspection. A 60-100x adjustable scope can be had anywhere online for 15 bucks.

Pistils change color very early sometimes. One thing to look for is when newer white hairs don't look so vibrant, kind of shriveled.