Shades of Gray is not a theme for WordPress itself, but a skin for the WordPress Sandbox theme. Shades of Gray is a minimalist, two column fluid-width theme. It is primarily a grayscale skin but could easily be modified to use whatever colors you desired. If you would like to play around with the skin in the wild feel free to download it and give it a try.
One of the most interesting themes for WordPress is the Sandbox theme. Sandbox is different than most WordPress themes due to its semantic markup and dynamic class-generating functions. The authors of the theme have leveraged Cascading Style Sheets (CSS) to allow for the styling of almost anything on the page without having to touch any PHP code. Nearly every HTML element has an assigned class. For example, multiple classes are assigned to the body and to every post. This allows designers to change the look and feel of Sandbox by creating different skins (CSS files) which are then applied to the theme.
After finding some WordPress themes for inspiration I set about creating the look and feel of my new site. As different developers will take different approaches to designing a site layout there are several ways to go about doing this. I believe that a solid theme will always start with well coded HTML. As a result, the very first thing is to create a homepage with no dynamic data, just a plain HTML page with code for the layout and dummy text as content. Then the look and feel can be applied to the site with CSS files, colors, and images being plugged into the static page.
The rational behind completing the site design/coding and layout first is to make sure that all of the code blocks are in the right place and semantically laid out. In addition, this is a good time to validate the site, checking for errors like an improperly closed div tag that could mess up the site layout. Once the layout code has been added to the WordPress template, errors of this kind are much more difficult to diagnose and fix. This approach provides a chance to nail down the styles that will be used for layout and text without having to worry about any WordPress tags or PHP code getting it the way.