To be 100% certain I would inspect the trichomes under a jewelers scope (recommend a 30x) .Milky trichomes prove to be the most psychoactive (as they contain the most THC) and amber will create more of a body high when regarding Indicas. If you are not able to obtain a jewelers scope, I would look for when the majority of the white pistils turn a red/amber/brown color and retract towards the bud.Then it is time for harvest.
Happy Growing