Paint/ trim codes are a bit all over the joint on these cars. On the trim line the first 4 tell you your paint colour (eg 1926) the next three are your trim (eg 18v). First number of trim is the colour, second is the shade, and the letter is the material.

I think the codes on the paint line are the Dulux (or whatever the brand was) codes, while the one on the trim line is the Holden code.