Question re: 8th army formation sign.

Now, I've always understood 8th army sign was yellow cross on a white background and a while ago i read in an official history of 121 field regt. RA that they had to put up an orange cross on a white background when they joined 8th Army.
At first I thought maybe he was colour blind or had mis-remembered, until I saw the attached pic at this website.
Any thoughts on this anyone?