'68 NEC 210-5. Color Code. Only a slight change to describe grounding conductor colors. The section, otherwise, is unchanged from the previous editions and still includes color specifications for ungrounded conductors of multiwire circuits.
'71 NEC 210-5. Color Code for Branch Circuits. The section is broken into parts (a), (b) & (c). Section 210-5(c) Ungrounded Conductor
is new and is followed with a fine print note:
It is recommended for a basic single wiring system that the following colors be used: 3-wire circuits, 1 black, 1 white and 1 red; 4-wire circuts, 1 black, 1 white, 1 red, and 1 blue.
'71 NEC 210-5(c) itself no longer specifies colors.
'75 NEC 210-5(c) the FPN is deleted and the wording is simplified to:
210-5 Color Code for Branch Circuits
(c) Ungrounded Conductor. Ungrounded conductors of different voltages shall be of different color or indentified by other means.