You can modify the contrast, fade, and monochrome settings of an underlay. Also, the underlay color can be inverted for improved visibility against the background color.
Adjusting these settings does not alter the original file and does not affect other instances of the underlay in the drawing. You can change the contrast, fade, monochrome, and colors in the Properties palette when an underlay is selected. You can also use the DWFADJUST, PDFADJUST, DGNADJUST , or ADJUST commands.
If you change contrast, fade, and monochrome values, plotted output is affected.
Adjust Colors for Background controls whether the underlay colors are visible against the drawing background color. The default setting of Yes indicates that the background colors of the underlay and the drawing environment are analyzed to see if they are both light or both dark, or is one dark and the other light. When one background is light and the other dark, the colors of the underlay are inverted so the underlay is displayed. If the setting is changed to No, the original colors of the underlay are used. Depending on the background colors, the underlay might not be visible.