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White & blue are the better steels.
Yellow paper steel is used for entry level kitchen knives & some high end tools. It is highly dependent on good heat treat tho for optimal results.

Last pics are some considerably worn Tosuke. The blue one has been honed into a smile. Not usual for kamisori.

The 2nd one has consideable wear & has been scraped with a sen (jp metal file) into...

Here are some Iwasaki with a few years of hone wear.
Notice that on the stamped side (Ura) it should always be miniscule.

The 2nd pic of the non stamped side (omote) shows acceptable wear for 5...

The red highlight is probably the best idea.

To buy second hand you need to know the maker's grind style eg the apparently large looking edge bevel on a Tosuke NOS could mean something was wrong...

They usually come in 45 , 50 & less often, 60mm lengths.
Handle wrap or no is up to you. I like the bare metal.

They can usually shave ok even with a lot of hone wear if you know how to restore...