here is a new DISKBOOT.BIN. The new version (sx120is-100b-0.9.9-884-svn23) contains another fix suggested by cppasm and the right value for PROPCASE_WB_ADJ, meaning that it is now possible to use the white balance value of the camera.
I'd be glad, if somebody could provide a better color matrix. I don't know if the right white balance value makes a difference. There should be instructions in the wiki somewhere...
For discussion, please go to http://chdk.setepontos.com/index.php/topic,4284.new.html#new