good lord thats one leafy plant, id say the best thing you can do is look for several tell tale signs. If you can grab a 20x jewelers loupe so you can look at the trichs that would help. Color of trichs arn't everything though. The red and white "hairs" need to retract into the plant, the bracts (the pods that would house seeds had the plant been pollinated) need to be swollen, and the trichs should atleast have a few amber colored so that you know they are reaching their peak of maturity however some strains just do not produce amber trichs, and even still amber trichs can appear on plants just from a bit of rough handling.