take off colas at certain percentage of amber you see... label it so you can distinguish it later when figuring out what you prefer.
take the bulk where you believe it will be -- what percent amber? For example, if you like couchlock / falling asleep weed let it amber up significantly when you take the bulk of the harvest. can always leave a cola to ripen more after that point too, if you think you'll prefer a more energetic high early on in harvest window.