I wrote a post that explains three settings that govern how AutoCAD files are created related to By Layer or By Entity.

• Category Properties ByLayer, overrides ByEntity - This deals with differences between elements that have the same layer assignment but "look" different in Revit for some reason)
• All Properties ByLayer, no overrides - This forces all exported elements to be ByLayer which will change line patterns and colors so that they ARE By Layer)
• All Properties ByLayer, new layers for overrides - This allows Revit to create a new layer when an element has a representation that a single layer will not support)

Thanks for reply, instead of checking i am asking How do linked ACAD details get exported back to ACAD from Revit. This was the original question i posted some days ago with no reply, Is there any control over colors by layer or by entity, when exporting linked cad details back to cad?

Regarding Export to DWG option: Export views on sheets and links as external references

• If checked imported DWG files will export as a native AutoCAD External Reference
• If NOT checked imported DWG files will export as a native AutoCAD Block Insert

Revit intends to respect the native conditions of a DWG file during export from Revit. The transaction is regarded as if there is no reason to import a DWG into Revit only to Export it right back to DWG. Instead it just passes the DWG file (intact) out and puts it back in the exported file as a native DWG xref or block.

Alright, i linked a same autocad file in revit and exported using different export configurations, and you are right that Revit respects colors and layers of linked files.
But 1 out of 5 samples was linked using Import line weights setting. I assigned line weight 1 to color 1, 2 to 2 and so forth upto 9 colors and layers were being linked.
The cad file got linked as expected with varying line weights with respect to the colors, but now when exporting the line with weight assigned 1 gets a color number 20, the line assigned weight of 2 gets color 210, 3 gets 170, 4 gets 130, 5 gets 90, 6 gets 50, 7 gets 10, 8 gets 250 and 9 gets white (which is 7).
This coloring is consistent in all sort of cominations of import or export, as long as i keep the line weight of imported colors 1 it gets exported back as 20. Is there any control to override these settings and let Revit epxport the linked cad file to respect the original colors (it does not change the layers though) to remain intact.