Hello,
Going by the trichromes is the most accurate definitely, but another good indicator of harvest approaching is the pistils. Your pistils in this photo look almost entirely white, once they start to turn orange and shrivel up that's going to be a good sign to be looking more into the trichromes. Once the plant has at least 50% or more i think you'll see much more color changes start happening in the trichromes. I saw one that has a slightly amber look, but you wanna be seeing mostly milky(80%) and then many amber ones, more than 20%.