There are several ways to remove the bluing, including some commercial products designed especially for that task. Vinegar will work very well; about a half hour's exposure is usually sufficient, but longer won't hurt if needed. Naval jelly is a good alternative to vinegar.
The color case hardening on the replica revolvers is cosmetic. Removing it is difficult but not injurious; the underlying material is generally hard enought to not require any additional measures. I have no advice on how to remove the color case hardening.
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