Kind of a loaded question lol but so are lots of things in growing. I would give it at least 5 days to a week minimum. flushing depends on the level of nutrients that have built up in the tissue throughout the grow. with that in mind, if your a heavy feeder and tend to push the PPMs towards the upper limit, your likley going to need more time for those nutrients to leach out of the plant. and if your a light feeder, you can flush for less time. the leafs changing color is one indication of how the flush is going, but I wouldn't go by leaf color alone.
as far as trichome color, there are lots of different 'methods' people use to decide when to flush/harvest, some people (myself included) prefer to do it when most of the trichomes are milky in color. Some people let them get to 10-20% amber before harvesting. hell, I have a buddy that wants at least 50% of them amber, but I dont recommend that. The school of thought here, is that the more amber trichomes you have, the more 'couch-lock' type high you will get. but it wont change a sativa to an indica, it'll just give it an indica 'lean' as I call it. I say it like that because the strain cant jump from one type to another, but it can lean more towards the effects of an indica if grown correctly.
Make sure you prepare your drying space, like now lol. It could seem early but drying and curing are CRUCIAL! You could have the dankest of the dank, but if its not cured right, or if its dried too fast, it's going to taste like sheep shit and wont do much for you. remember that light and air degrade THC, so you want your buds in a dark place with decent airflow, be sure your not pointing the fan directly at the buds. you want air circulating through the room As a grower, the best way to learn is experience. Don't be afraid to try something new. if you fail, consider it a lesson learned and move forward with your head held high, amigo!
Best of luck to you! stay red eyed, smiley, and live life irie!
