The Update Drawing Layers to Match Project List command is used to update the layer definitions on the drawing. Once a layer is created on a drawing, it is not modified. Changes you make to the color, lineweight, or other attributes are not overwritten. This command is the only way to modify layers that already exist.
To update existing layers on a drawing to match new definitions in the project list, go to
Ribbon: DME: Customization->Project Customization-> 
Update Drawing Layers to Match Project List
Pulldown Menu: DM Electrical->Customization->Layers->Update Drawing Layers to Match Project List
The layer definitions on the drawing will be updated to match the definitions in the project list.