When exporting a DWG file it originally has colors defined by parts created in AECOsim Building Designer, where the colors are often applied ByLevel. Once the model is exported to DWG it shows the correct colors, but if updated according to the DGNlib it will now display the wrong color with no easy way of reverting back. I believe this is because the color table is different in DWG, and if the software wants to reapply the color associated to a certain number it will be different if the color table has changed. How can I get the colors to display as intended if an exported DWG file is unintentionally updated?
AutoCAD DWG files only use one color table. When we convert from DGN to DWG we match the colors based on the RGB color value. This causes the colors to look the same but the color numbers will change. For example, the standard AECOsim Building Designer color 1 is blue, and while saving to DWG the color remains blue it changes to color number 5. AECOsim uses color numbers in both DGN files and DGNlib files. So, when we update the level's color, we update it to the color number used in the DGNlib file.
For projects that will be converted to DWG, use the delivered AutoCAD color table ACADCOLOR.TBL from the start in your DGN files. Also make a copy of the DGNlib file and use the AutoCAD color table in that file as well. Set the colors in this DGNlib file based on the AutoCAD color numbers.
The only way to prevent colors from changing is to use the same color table in your DGN files, DWG files and in DGNlib files.