You may have already seen this, but we had quite a discussion on the color codes, past and present, of various countries. The thread is here
with a condensed summary posted in the technical reference section here
These just go to show that what might seem to be an "obvious" choice of colors to somebody who grew up with them, might not be to somebody else.
In the West we accept red and black as common colors for positive and negative on D.C., such as on test leads, but I have a Russian-made meter which has white and black leads and probes (I still have no idea which way round the Russians use them.)
On the D.C. issue, here in England black was adopted for the grounded pole of a D.C. system (as it is with A.C. systems). Red and blue were then used for D.C. lines positive or negative with respect to ground on a 3-wire system, but our "code" for building wiring specified that the hot pole of a 2-wire DC circuit should be red, even where it waa derived from the negative
side of a 3w DC system!
You can see the red/blue coding on D.C. switchgear on the London Underground (subway system) and elsewhere. For example, in old G.P.O. telephone offices the positive (grounded) busbar was bare while the negative busbar was identified blue.
I too would be interested to learn when the common American colors came into general use, and/or when they were first specified by the NEC.