You are close but let me expain little more clear on this one
majorty of 3Ø breaker box the bussbar arrangement is A-B-C if you look from the front the letter is left to right arrangement expect the I Line and few other the buss read 90° around it will read from front to back and also a warning here some two pole breaker and some single pole breaker may land on diffrent phase squenice espceally with some of the two pole breaker I know I deal with on the I Line series on two pole breaker it will have AB , BC or CA format it may throw you off the track when you do the set up
for the normal numbers I useally sum it by 3 unless you have oddball arrangement then go either 6 or 9 depending on the set up.
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)
The rythym is Black, Black, Red, Red, Blue, Blue at 208Y120.
This is repeated seven times in the typical three phase panel of 42 circuits.
1,2 Black 3,4 Red 5,6 Blue
The colors shift if we're talking 480Y277 But the rythym stays the same.
IMHO this is the easiest way for you to do it. You are on the right path with the divide by six and then use the above chart with the remainder. I only added one change to it though.
1,2 Black **** Brown 3,4 Red **** Orange 5,0 Blue **** Yellow
You divide the circuit number in question and then use the remainder to find the circuit color.
64/6 = 10 full times with a remainder of 4. Check the chart and 4 is red or orange.
30/6 = 5 full times with no remainder so the 0 is used. So it is a Blue or Yellow circuit.
87/6 = 14 full times with a remainder of 3. 3 is also a red or orange circuit.
I hope I explained as close to the way I learned it. Seems easy for me, may not for others. Great part of this trade is we take from others things we can use, and sometimes it works and sometimes it doesn't.
LMK if I can explain it any better.
"If common sense was common, everyone would have it"-not sure, someone here
On dimmer racks, the busses are separated by phase, so it's easy to tell which dimmer (circuit) is on each phase. It's not as easy to find a dimmer by number, as the numbering from top goes 1, 2, 7, 8, 13, 14, etc.