changed bg color to gray
changed bg color to gray

Signed-off-by: Andre Klein <bfabf9658fe7716c8fd9ec60657cc91b04a4cb63@dkfz-heidelberg.de>

fmilano/mitk,fmilano/mitk,MITK/MITK,fmilano/mitk,MITK/MITK,MITK/MITK,fmilano/mitk,MITK/MITK,fmilano/mitk,MITK/MITK,fmilano/mitk,fmilano/mitk,MITK/MITK