To summarize, Shapton Glass 500, 1,000 and 2,000 is a good combination and if you would like to throw in the 4,000 grit stone in lieu of the 2,000 that is good as well. If your knives are very hard, ZDP 189 for example, this is a fantastic choice. (They are also excellent for tools, chisels etc. and they are the premier choice for many Straight Razor honers).
Mine came plain white then started to darken after a few weeks. About 4 weeks in it settled to a more natural stone/slate grey. The leather has darkened a bit too and remains soft and comfortable. The leather remains easy to adjust and my selected sizings stays in place firmly. Overall It feels, looks and works great. The knot and darker stone/leather compliment each other well.
Vielsalm Coticule on the other hand generally occurs in much more narrow layers sandwiched between the slate layer and the Belgian Blue layer and thus, it is both less plentiful and more expensive than Belgian Blue stone. Also, Coticule is divided into different grades and sometimes displays blemishes on the surface due to its proximity to the slate layer. Furthermore, it is somewhat harder than Belgium Blue stone and, due to its brittleness, it is bonded to a substrate layer of hard slate prior to sale to prevent the stone from breaking during use.
The truth is that there is no one recommendation that we can make that will meet everyone’s needs. Every sharpener’s needs are different and every sharpening toolkit will be different. In order to help beginning sharpeners get started with good sharpening stones to build around, we need to understand their individual needs. So with that in mind, let’s look at the basic needs of a beginning sharpener.
Steeling helps maintain sharpness. This process realigns the edge, correcting for dulling causes such as a rolled edge. A sharpening steel is a type of hardened cylindrical rod used similarly to honing stones. For example, a butcher steel is a round file with the teeth running the long way, while a packer steel (used in the meat packer's industry) is a smooth, polished steel rod designed for straightening the turned edge of a knife, and is also useful for burnishing a newly finished edge. Because steels have a small diameter they exert high local pressure, and therefore affect the knife metal when used with very little force. They are intended for mild steel knives that are steeled several times a day, but are not well suited for today's tougher and harder blade steels. Diamond steels are now available that have an industrial diamond coating and can remove blade metal as well as straighten, therefore used correctly they can re-profile a knife instead of just honing.