Is there an online example of all the colours in System.Drawing.Color?

From here:

The following image shows the color of each predefined brush, its name, and its hexadecimal value.

May as well have the details right here on SO:

"Web Colors - X11 color names" from wikipedia:

http://en.wikipedia.org/wiki/Web_colors

http://en.wikipedia.org/wiki/X11_color_names

WPF Colors

Color names in Windows Presentation Foundation (WPF) match the color names in Microsoft .NET Framework, Windows Forms, and Microsoft Internet Explorer. These colors and their names are based on the UNIX X11 color values.

http://msdn.microsoft.com/en-us/library/system.windows.media.brushes.aspx