As I understand it, ACAD also uses colors mapped to colors, so you will need to get that color/pen table from them, and then you need to create the DcadWin.TBL file that gets the correct "roundtrip" colors.
Are you working for them, or are they working for you?
The DcadWin.TBL file is related to the DcadWin.RGB file, and it translates the DataCAD screen colors to the ACAD screen colors, and back again. This way, you work in the colors that you want to, and they work in the colors that they want to, and you both get the plotted lines that you need to.
We made a pen table in AutoCAD that matches our pen tables we use in DataCAD. When we send files to the engineer, we ask if they would like the matching pen table for AutoCAD so they don't have to spend time creating things we already have.
We also take our hatch patterns and use HatchKit to save them in AutoCAD format so everything goes back and forth smoothly.