As a result of adopting the U.P.U colour scheme in January 1922, ‘blue’ became the foreign letter rate. This was reflected accordingly with the colour change to blue of the 4d KGV on 22^nd March that year. However, it took until December 6^th 1923 for the residual stocks of 6d blue kangaroo to be used up. At which time its colour was altered to brown.

Naturally, the new colour appears on the same (new) Harrison Die 2B plates, and on the same watermark as previously.

A small change had occurred however to the imprint. The lower plate used a new 'N/M' style, which was subsequently inserted into the upper plate as well after the 1st printing.