Translate old colour codes

[Magnus Forsberg]

I have to come back to the original question, following the findings in this question.
"Is there a way to 'translate' the old code to a new code?"
I want to fix the parts in Niko's list, but I feel very confused now....

ColourSum makes it easy to blend two known colours and helps in finding the nearest LDraw colour, but I can't use it to revers the dithered colour code into a new RGB-code. Or can I?

The same two base colours will give two different dithered codes.
Take two base colour codes, like 7(Lt Grey) and 13(Pink).
If I feed them into this equation

Code:

nb = n1 * 16 + n2 + 256

I get two different dithered codes, 381 or 471, depending on if I set n1=7 or 13. Both looks to be the same shade of pinkish in LDView.

But I also find pairs of code that show different colours in LDView.

Code:

1 381 0 0 0 1 0 0 0 1 0 0 0 1 rect.dat
1 471 2 0 0 1 0 0 0 1 0 0 0 1 rect.dat

1 349 0 0 2 1 0 0 0 1 0 0 0 1 rect.dat
1 469 2 0 2 1 0 0 0 1 0 0 0 1 rect.dat

1 382 0 0 4 1 0 0 0 1 0 0 0 1 rect.dat
1 487 2 0 4 1 0 0 0 1 0 0 0 1 rect.dat

  dithered.png (Size: 23.95 KB / Downloads: 3)

Are all the dithered codes paired in two, and why do I sometimes find they're not.
Is it true that code 381 = 471, and should show the same colour?

Why do the same code look very different in LDCad?

There must be some more mathmatical magic involved here.