If you do any Silverlight development, you'll likely end up spending a good deal of time switching between Expression Blend and Visual Studio. Blend is the designer tool that lets you build the pretty XAML interfaces in a WYSIWYG mode. The UI in Blend is distinctly different from Visual Studio, with mostly black backgrounds. When you switch over to Visual Studio to write your code, it can be quite jarring on the eyes moving to the code-editor with it's mostly black and blue text on a white background.
If you've played around with Ruby on the Mac, there is a color scheme for TextMate (a code editor on the Mac) that is popular called Vibrant Ink. This scheme features white, orange, and green text on a black background. John Lam, who is leading the IronRuby efforts at Microsoft, created an equivalent theme for Visual Studio back in June. I learned about it recently while browsing Rob Conery's blog. Rob is the creator of the SubSonic framework on .NET. He recently posted his own tweaks to the 'Vibrant Ink' theme released by Jon Lam.
I've loaded this theme into Visual Studio on my machine and am going to give it try the next couple of weeks. Hopefully it will be less jarring on my eyes (which seem stressed lately from using the default 1900x1200 resolution on a 15.4 inch laptop screen). The only thing I've found off the bat is that the colors don't map so well for XAML. Instead of the 4-color default scheme for XAML, it appears you only get a 2-color scheme one there. I suppose if it annoys me enough, I can go figure out how to update the theme to get more colors back. Although, I hope to not be editing XAML a lot in Visual Studio since that is what Blend is for!
After you pick up the .vssettings file from either John or Rob, you can easily import it into Visual Studio with the import instructions here on MSDN. Give it a try and let me know what you think. Also, if anyone tweaks it to have better colors on the XAML files, let me know!