Follow the example that i<3bush provided. I wanted to pull the rip cord on my plants when the buds looked similar to what you have. I would have stopped way too early. You have between 2-4 weeks. Dont trust your eyeballs. Get a magnifier. Take some samples from the tip, the center, and the bottom of a few buds. Average the results. You have done a great job so far! Finish strong. Dont forget to flush the plant before you harvest.