Here's my experience--only broken in 1 barrel 'properly', a benchmark 30 cal. Just did this last month.
I did the shoot 1 / clean 1 approach for the first 10 shots. Then, I fired 3 shot groups, cleaning after each group.
The patches were a dark, vibrant blue for the first 5 shots. The 6th patch did not have this dark, primary color blue. Thereafter, the shots were more bluish-green and lighter in color. Once I hit the 10-20 shot range, I saw no difference in patch color--just a light blue-ish green. I cleaned with Butches, but now use Boretech eliminator.
I used the same 150g soft point ammo for the break in. Around round 20 I fired some 180g accubond handloads. I cleaned the barrel after firing the first handload. The patch was that dark, vibrant, primary color blue. Subsequent handloads did not have this primary color blue, but exhibited the light blu-ish green color.
I don't know if the break in made any difference, but I did observe a difference in the patches going from primary color blue to light blue-ish green, and I haven't seen this primary color blue since.
So something was changing in the process. I called the good folks and benchmark who said that once the barrel is effectively broken in after that dark blue stuff is gone.