Light Switch Neutrals: Bundle all together?
Wire nuts are color coded by size.  A yellow nut would be fine for 3 wires, but at 5, you'll want to go to a red nut.  If it won't stay together without tape, that is bad technique that will cause arcing and fire - fix the technique, don't tape it.



That "gray" wire you are seeing is actually black that is poorly tinted or faded.   Actual Gray is a middle 50%-ish gray, and is legally reserved for neutral.  

Hots can be any color but white, gray or green.  However, in practice, using cable black is preferred for always-hot, and red is preferred for switched-hot.   In practical practice, we are stuck with the standard colors that come in cable, but "red" for "switched-hot" often works out.   Of course in a 3-way circuit, all bets are off...



As for box fill, there are rules on that. Count all grounds as 1 wire, all cable clamps as 1 wire, each "yoke" (switch, receptacle) as 2 wires, then count each non-ground wire entering the box.  Do not count pigtails.   Take that sum, multiply by 2.00 for 14 AWG ... or 2.25 for 12AWG ... And that is the number of cubic inches you need in the box.  If the box is overfull, you need to fit a box extension of some kind.