There’s also a Hitachi Yellow Steel series which you don’t hear of that much outside Japan. It’s used for more mid range cutlery and basic agricultural edged tools. It looks similar in composition to 1075/1084/1095 etc.
The White series is ‘cleaner’.
White No. 2 seems to be the standard quality carbon cutlery steel in Japan, with White No. 1 being used for high end applications.
Here’s a pic I took of some steel bar stock at a bladesmith’s forge in Sakai:
You can see they use coloured paint on the end of the billets these days, instead of paper to indicate the grade.
Interestingly, when I had an opportunity to ask the kamisori master, Mr. Iwasaki in Sanjo, what kind of steel he uses for his straight razors, he said he actually favours one of the European White Steel No. 1 analogues made with Swedish iron ore, rather than the local Japanese product.
Might have been 26C3 or 125SC. His father was a metallurgist too, so no doubt he had some sound reasoning for that preference.
To the OP, you'll also see the White and Blue Paper steels referred to as Shirogami and Aogami - literally the same thing in Japanese.
Sal's mentioned before that one of the design applications for VG10 was for grafting tools in the horticulture industry.
One of the other original design parameters of Takefu's VG10 was to create a steel which could be used for sujihiki and yanagiba knives in commercial fish and seafood processing settings like the vast Tsukiji market in Tokyo. The steel needed to deliver similar or better performance characteristics to carbon steel, with the added benefit of stainless corrosion resistance.
It's worth remembering that despite many Western steels not being designed specifically for cutley, most of the Japanese steels mentioned by the OP are cutlery specific steels. I'm not sure about Super Gold/SG2/3G, but the White Steels, Blue Steels, VG10, and ZDP189 were all designed for high performance knives and other edged tools.
