One MSDN resource I use regularly is the page about named colors.  It is helpful when I want to quickly add a color to my application without going through the RGB color picker.  This reference is good because it provides a screenshot example of each named color, along with its official predefined color name and corresponding RGB values. 

This page is part of the Silverlight 1.0 documentation.  I use this one because I haven't found a similar reference for Silverlight 2.  Besides, the 1.0 color names still work in Silverlight 2.

It would be cool if Visual Studio provided color swatches in the IntelliSense.  Here's the current IntelliSense:

Here's what it could look like:

Neither Blend nor Design support setting colors by their named values.  Of course, you can do this in XAML in Blend. 

Perhaps the lack of support for named colors is because most "real" designs will use colors defined by their RGB values.  It would still be cool to have this resource integrated into the tools rather than having to look it up from documentation.