Why white regions are blank?

I have created several 3d regions that are supposed to be white.

When I change the visual style to realistic, the index color white is blank.

When I change the color to true color 255,255,255 the object is white.

Why is this?

Thanks

Because color #7 is a variable color depending on your background color. It displays as white on a black background but will display as black against a light background. If you change your background to grey or white you will see black lines, not white lines. If you want the color white, then you need to use true white, color 255, 255, 255.

http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=8008602&linkID=9240615

Thank you for your help