Some strains change the hair colour almost all the way like 4-5 weeks before harvest. Ive seen this with some sativa dominants.
Trichomes are the sure way to go.
100 % clear = still cooking thc n stuff
100 % milky = peak thc
80% milky 20% amber/brownish = yummy, yummy, harvest time
It is up to taste, speedy head high 100 % milky. More all around high the 20% amber sweet spot.