There are several ways to color concrete. It can be added at the plant so the color goes throughout, it can be applied in powder form to the wet concrete in place or the concrete can be stained after it has set. Typically the second method is used with stamped concrete along with a release agent but all three methods will work.
I wouldn't worry about the forms but it's risky to wait so long before cutting control joints. Tension from shrinkage starts developing in new concrete soon after it is placed. Since the concrete hasn't developed much tensile strength yet, shrinkage cracks are likely.
The purpose of control joints is to relieve the tension by encouraging the concrete to crack where you can't see it as opposed to forming random surface cracks. Ideally these joints are grooved during placement or cut immediately after placement with an early entry saw.
The longer you wait before cutting control joints, the more likely you'll get surface cracks. The likelihood of this occurring depends on a number of factors such as the size and shape of the slab, the concrete mix and slump, weather conditions, etc.
I'd carefully inspect the slab (the cracks might be hard to see early on) before I made final payment. I'd also make sure the concrete comes off the adjacent surfaces without damage. I think you might be right about the competency of the crew.
