So you are looking for a utility that maps the RGB value of an element to a new color table index. It does not have to be ACAD color table, any color table. I don't believe that MicroStation currently has this tool but I won't be surprised if someone out there may have a VBA or MDL program that does similar remapping.
There is a delivered AutoCAD color table you can use. From menu Settings->Color Table->File->Open, by default you should be seeing color tables available under \Workspace\system\data\. Open acadcolor.tbl to use this table.
Don, yes I'm aware of the table, which I would like to use. But attaching the table will not reassign color numbers to the elements. Saving to dwg does a good job of reassigning color numbers to the appropriate acad color. What I would like is to reassign color numbers to closest dwg color match without having to save to dwg then save back to dgn.
Don, Yes it could be any colortable. Obviously the coding for ACAD has already been done. Ideally if you attached the ACAD table (or any table) it would prompt if you want to assign the element color # to the new equivalent. Also on this wish list would be if you are using the ACAD table or are in DWG mode that the color picker use the ACAD layout rather than the 16x16 grid.