Hi

Here are some pictures:
http://hot.ee/sonnich/scan1a.jpg
http://hot.ee/sonnich/scan1b.jpg

A is the original picture, 50% in order to make it fit here.
As you can see only a part of it is in the right colours.

A part of the original scan is the B - with "waves" in it, I have seen
that before and know simply to resize. But you can see the colour
difference better.

What causes the yellowness and how can I fix it?

It is a HP Scanjet 2400.

WBR
Sonnich