Its simple. you DO NOT look at the colour of the pistils. This is not an accurate measure of the plants potency.

You get a $5 60x microscope with LED lights on it. You need to look at the trichomes. When the plants is premature the trichomes will be clear.

When the plant is at full THC capacity all (most) trichomes will be milky or cloudy.

When the THC begins to break down into CBD the top of the trichomes will begin to turn amber.

It is good to have a certain degree of amber before you harvest.

With all trichomes clear you have harvested too early.

With all trichomes milky you will have a more heady, energetic high.

With 20% amber / 80% milky you will begin adding more of a body high to your energetic high.

With 50%+ amber you will begin to get more of a body high. Stuck to the couch kind high.

The trick is to find the stone you like by watching the trichomes. You can harvest the plant in 3 different stages to see what you like.

I prefer to wait for 30% amber / 70% milky before I harvest.

Take care.