well, it seems we are stuck with the color problem for now. currently, I am using the color matrix taken from the SX10 port; the sensors seem to be identical, and it yields acceptable yet far from optimal results.
if somebody can come up with a better matrix, you'd be highly welcome to post it here. theoretically, it could be found manually using dng4ps2 if you have the time and/or skills...
1) take a picture of the color checker chart as described here: http://chdk.setepontos.com/index.php/topic,390.0.html
2) convert the raw image from 12 to 10 bit with this tool: http://ewavr.nm.ru/chdk/12to10.zip
3) install dng4ps2: http://dng4ps2.googlecode.com/files/dng4ps2-0.2.3-beta20.exe
4) create a new camera with the following data:
Camera name: Canon DIGITAL IXUS 970 IS / Canon PowerShot SD890 IS
Short name: IXUS 970 IS / PowerShot SD890 IS
Sensor size: 3720 x 2772
Jpeg siz: 3648 x 2736
Act zone x1,y1: 6 , 12
Act zone x2,y2: 3690 , 2772
B-w levels: 31 - 1023
Mosaic type: Red, Green Green, Blue
Matrix: 0,827547 -0,290458 -0,126086 -0,012829 0,530507 0,050537 0,005181 0,048183 0,245014
5) calibrate the camera by altering the matrix values. check them by converting the color checker raw into dng, and comparing it to the jpeg produced by the camera.
it is possible that somehow the automatic calibration might work, but both ewavr and me failed so far. ewavr discovered that if you leave out some colors, it might work - but thats very un-desirable. the matrix posted above might be a good starting point.