Well, how we do it, Blue goes left of the boss, the other to the right. All team leader had to do was say for you to go left or right, as there is plenty of time between bethered tethered to the boss and the tethers linking you together for someone to tell you in voice. Just stand out a bit from the tail when tethers are due so easier to note what color you have as the tail can obscure XD If just 1 tether, we stay behind the boss.

Not timed it, but it must be around 5 seconds from being tethered to the boss till being tethered together.