Based on the MicroStation V8 file format, element colors (0 or 7) are manipulated differently at plot time. By default, color 0 (white) is plotted black within a native MicroStation V8 file. DWG/DXF formatted files, by default, contain color 7 (white) and MicroStation must manipulate the color data to plot it correctly. The following will explain the different file format scenarios and how white elements are plotted.
If the file format in use is DWG or DXF, and the file DwgPlotColors.tbl can be found using MicroStation variable MS_DWGDATA, the auto invert color is always 7. In addition, we invert color 0. Normally, DWG/DXF files do not contain any data using color 0.
If the current file format is DGN, the MicroStation printing workflow will check the original file format. If the original format was DGN, then the single auto invert color is always color 0.
Otherwise (for original DWG/DXF files resaved as DGN files), the auto invert color depends on the color table in the model. MicroStation checks the values of the background color and color number 7. If both are near white (all RGB components >= 250), then MicroStation concludes the default AutoCAD color table is still in use, and the single auto invert color is 7. Otherwise, the color table has been modified and the single auto invert color is 0.