I have worked with dry color for concrete. We poured a few slabs and some curb.
The dry power was available at a concrete supply house. It was expensive, but could be bought in small bags if needed. A little went a long way.
The color powder made a huge mess and stained everything. It was the consistency of powdered sugar. You need to mix it really well with the dry mortar or you will end up with varying color. You need to test the color by mixing up and curing a sample as it is hard to know exactly what the color will look like until it cures.
In this case, I would skip the color and use polymetric sand. Something like this: http://alliancegator.com/2011/?p=21
The best pry bar model that I know of for lifting concrete slabs is "big" (as in, the bigger, the better). Use a block of wood or something else that's large, to distribute the weight on the ground, for your pivot. You'll likely have to dig out one, if not two sides to pry and maneuver these blocks. Avoid putting too much pressure on a single point, since that can cause the paver to crack.
For the level, away from the house is good if this is draining against the foundation. You don't need much, but keep it consistent by using a level and measuring the rise over the run.
When resetting the paver, don't just build up one edge. That would leave an air gap in the middle that can result in cracking. Don't disturb the ground below the paver other than to remove any high spots, you don't want it to settle after you're done. Just add stone dust to make a level surface. Then replace the paver, wiggle it a little to work the stone dust into a tight contact, and replace any ground that you dug out from the sides.
For weeds, I'd ask over on the Gardening Stack Exchange, but they make lots of weed killers. You can also place a barrier in the ground, or just go with hand pulling. I've also seen suggestions to mix some cement and sand, brush it dry into all the cracks, and spray it with a light mist of water, but that would make any future repairs very difficult.
Best Answer
Use a non selective herbicide to kill off the weeds, give it time to get to the roots and destroy them too so when you get a power washer, it will clean EVERYTHING out. Dirt that got in there for the weeds to start on has got to go. The roots that are buried in the cracks will decay and turn to dirt too over time, that is why the herbicide has to have time to work before the power washing.
I would not use caulk here. It will look like stripes are everywhere, and they will not look good. Use masonry cement to fill the gaps in a few different consistencies. Mixed thin for small cracks so it can get forced in easily, thicker so it can stand up in places, like in the front of the steps in larger crack so it will not slump out.
After the work is done and it is time for cleanup, which it will be mess, I use a sponge that tile setters use, with a half filled 5 gallon bucket of water. The sponge needs to be dampened enough to be wet, but wrung out enough so it does not leave a wet trail while wiping. Damp trail only, a wet trail will re-saturate the mortar and will weaken and even possibly have it running back out of the joints you have repaired.
Use a masonry slicker to tuck in and finish the joints.