You might want to ask why the sawcut finishes half way down the slab.. Its there to encourage a crack.. The crack will keep going beyond the sawcut. QAnd while they are doing that, they didnt put an edge on the concrete so should run a concrete saw around the edge to make it look neater. Its a rookie job, coloured concrete is not forgiving.

Hi.. Grinding is not the answer.. although it would definitely work. You only ever see this on freshly poured concrete, Im pretty sure over time it will all be the same colour.. You could try speeding up the process with some white vinegar. Give a section a scrub and check out the results before doing a large area. Its just salt that is staining your concrete.