As mentioned below, personally I tend to wait for about 25 to 30% amber color trichomes. A majority of the remaining trichomes should be milky at that point. Also, I bought a great wireless microscope from Amazon for about 30 bucks. Great investment.
https://www.amazon.com/dp/B07DVFBVPF?psc=1&ref=ppx_yo2ov_dt_b_product_details