Color that goes all the way through
Because the pigment is part of the batch, integral color survives a chip, a scrape or years of foot traffic wearing at the top layer the way a surface finish does not. A gouge in a stained slab shows the gray concrete underneath. A gouge in an integrally colored slab shows the same color it started with, just a little lower down. That is the entire case for choosing it over a surface treatment, and it is the reason it costs more: the pigment has to be batched at the plant rather than brushed on after the fact.
Where the color moves, even when nothing was done wrong
Cement itself is not a perfectly uniform material from batch to batch, and pigment is measured against that variable base, so two loads mixed on different days from the same supplier will not reliably match exactly. Add water at the site to loosen a load and the pigment concentration shifts with it, which is one more reason not to do that. Weather during the pour and the cure changes it too. A slab poured and cured under hot sun finishes lighter than one poured in cooler, shaded conditions, even with the identical order going into both trucks.
A patch poured months or years later
This is where integral color gets misread the most. A section repaired or extended later is a new batch, on a new day, in different weather, and it will not reliably land on the exact shade of the original pour next to it. That is not a defect in the material or a mistake by whoever poured it, it is what happens whenever two separate batches of colored concrete meet at a joint. Anyone planning a repair or an addition next to existing colored concrete should expect a visible line where old meets new, not a seamless match.