You will want to wait until those balloons look like they are so full they look like they may pop!
If hairs (stigmas) are all white and sticking out straight don't harvest (they have low levels of THC and CBN).
If at least half of the hairs have darkened and balloons (trichomes) are half cloudy and half clear and are harvested, buds will produce a more speedy (trippy) energetic high.
If hairs are mostly darkened and balloons are mostly cloudy (milky) the buds have reached their highest THC levels. (High should be euphoria and pain reducing.)
If you let the balloons get (more than a few) amber, you will get (slightly) less THC and more CBN.
(The high will be more narcotic/ relaxing and anxeity reducing.)
This seems to be with all my strains.