Symbolizing CAD features
When you add CAD data to your map, ArcGIS attempts to reproduce the original appearance of the source file by rendering default symbology. Properties such as font names, color, and line thickness are read directly from the CAD file. Proprietary and vector-based fonts that do not have an ArcGIS equivalent are substituted with the Arial font. Line symbols unique to AutoCAD or MicroStation are defined with the style file ESRI-CAD.style.
Changing CAD symbology
You can change the default CAD symbology without converting the CAD file to a geodatabase format. Use the Symbology tab in the Layer Properties dialog box to change linear and point features. Use the Fonts tab to change CAD annotation features.
You can restore the default CAD symbology in the Symbology tab. If you save the map, your changes are saved in the current map but do not affect the display of CAD symbology in other maps.