The short is it’s your choice and everyone will give you a different answer but very few have dug into the deep and actually seen what research has been done on the topic so most opinions will be from word of mouth experience.
When your looking at tricombs for maturity there are two things to be aware of, first and most importantly is the shape. Your looking for tricombs to all be like mushrooms with nice caps/heads on them, if the head is not big and round yet then the tricomb is not mature yet.
As far as potency goes this is the single most important factor you can alter by harvest point.
Here is an informative paper
The second thing you have to decide is the type of high you want as well as how prone the user is to paranoia. This will help you choose the later factor which is harvest color.
You see Amber is the presence of tch that has degraded into CBN which gives you a more sedative effect, although it doesn’t mean that thc has stopped producing or is being degraded faster than it is being produced so keep this in mind.
I’ve harvested many strains very late with 30-60% Amber and enjoyed the highs, still not found them over couch lock (alot of effects do come from genetics and potency as well)
This all being said once you start to see Amber and have few clear left it’s generally a safe time to harvest if you don’t have much experience yet.
If your growing an indica don’t be afraid to let it run longer it will end up being stronger and more heavy of a stone. If you have a nice hybrid or a sativa then it’s a different story.
I would strongly suggest you buy a cheap amazon USB microscope and take some much clearer, more zoomed in photos so we can see the shape.
If you notice here the shape. Is much easier to see, we can also see just because the head turned Amber doesn’t mean the stock has turned Amber so keep. These variables in mind.
But that’s just some of what I know and I’m no professional or scientist.