Its a good question, and without a lot of testing there is no way to be certain, but my first thought is that Federal would try hard to make them exact in the explosive and burn characteristics even there is a color change.
Im also of the 1st opinion, that no matter how proficient, diligent, and consistent anyone of is as a reloader, the minor differences, in reloading 20 to 100 or more cartridges will still
contain more standard deviation in velocity than that caused by a manufacturing process that changes only primer color.
If you weigh all your bullets, you will likely see what I mean...
If you measure water volume in all your brass, you will see issues there too.
Are all the cartridges exactly the same length after trimming?
The list goes on. But load 20 new, and 20 old and get the Zero out and see if Federal has made a big boo boo. Then do it again to see if you get the same results.
The issue is gonna be extent of
standard deviation, whether its always in the same direction and whether its re producible and whether its a big enough sample size to be statistically valid.....
Sort of a headache right?
Trade all the new ones for old ones.....