The idea of completing an entire honing progression using only one stone is an exciting concept, but in reality it lacks practicality as you may find that while it may work for some razors, it will not cut a bevel for others; and in my experience with the system the latter applies, or more accurately the latter applies because of time limits.
As to colours, you are taking a risk no matter what. I have had a pink ish coti that cut quite quickly but didnt finish nicely enough for me. It would perform at perhaps 3k level with slurry and could set bevels. I have had a green coti with white streaks that could not set bevels. It simply would not cut. It was however, a very nice finisher. The only coti I ever kept was better than both put together. A rapid cutter that can turn slurry black, yes black after 20 circles. An awesome finisher en par with my Eschers. Vintage, a very modest 4 x 2 inch, deep yellow in colour with lots of black streaks. The smallest one in the picture and a true gem. It really is lightning fast - some of the guys at the UK razorcon witnessed its performance. Whats unusual about it is it also finishes very nicely. The green one I referred to earlier is the top one. The middle is a very 'average' coticule.
So it really does vary and I think while the general colour group/vein may apply, its a natural and you're taking a chance. Unless its tried and tested like Bart's coticules, its like a Kinder surprise, u just never know...
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