The color of the pad denotes it's coarseness but there is no standard so different manufacturers use different colors. You want to use the least course pad you can to achieve the desired effect. Too course and you will have to go over it again with a less course pad. Graining is just putting scratches onto the surface. Ideally you want them to be straight and parallel. You do not need any liquid but some owners find it helps. For regraining you start out with 80 # sandpaper and work your way to finer pads. Use masking tape to help keep you lined up and straight. For general cleaning I wash the car using car soap (very mild soap that easily washed off). For spot cleaning I just use Windex or alcohol to remove dirt or fingerprints. If you use a blending pad (Scotch Brite) you will notice the area is "brighter" than the surrounding area. You have removed the surface oxidation so it is shinier. That results in having to do the area next to it and so on until you have done the whole car. Or you can just wait a few days for it to naturally dull down.