I'm not a concrete contractor, but I did have a neighbor that had dyed concrete  poured, and it ended up with some splotchiness. Unfortunately, the fix was to rip out all the concrete and repour it.  In their case, it wasn't too much total concrete and the contractor ate the cost to make it right.

It could be many reasons hard to determine the cause from the picture. I would call another company specializing in concrete and see what they say seeing the issue onsite.

Was/is there a local architect involved in this project?

No, No architect involved

GN Builders L.L.C's comment is your answer.

We had stamped concrete around our pool deck. the only time it looked good was the few months after it was sealed. we sealed it annualy

Thanks everyone for your input.

Looks much better!

Looks great!  The color variations make it look even better as a stained surface, versus all just one solid color.

Concrete contractor here, stamped concrete has to be cleaned and sealed after pouring. Color does not work without the treatment. Didn't your contractor tell you this?

Anyhow, you will have to keep up on it, one of the downsides to stamped concrete.