tiff is shown in grayscale

[Carsten Keßler]

Hi,
I'm using a number of shapes and a tiff to generate the ouput map, with
MapServer 4.2.0 on Windows. The original tiff file is in RGB mode, with
8 bit per channel. The shapefiles are drawn correctly (in color), but
the tiff is only in grayscale on the output maps. This is the part of
the map file which defines the tiff layer:

  LAYER
    NAME basemap
    TYPE RASTER
    DATA rectifyos.tif
    CLASS
      NAME 'Basemap'
    END
    METADATA
      WMS_TITLE "Basemap"
      WMS_ABSTRACT "Basemap ..."
      WMS_SRS "EPSG:31467"
    END
  END

Any ideas what might be wrong with this, or with the tiff itself?

Thanks,
Carsten