In the field "Document window background", you can define the background color of the document window. The edit field "Intensity" defines how intensive the colour should be. We recommend you to not choose a very flashy or dark colour, because the hard contrast to the white document page background could tire your eyes. The option "Automatic" leaves Calamus to set the colour. On black&white screens you will get a 25% grey raster, and on colour screens the background will be set to light grey.