This is the Bluemarine theme that was included as part of Drupal 6, 5, and 4.7 (and maybe beyond) core. It was removed from Drupal 7 core, but it continues to live on as a contributed theme at this location.
It is a classic table-based, multi-column, recolorable theme that goes against all modern semantic, responsive, etc. design, but works very well as a utilitarian theme. It is good for when what you want is to display information in a neat and clean way, and you don't care too much about whether the display is pretty, frilly, or fancy.
This version of the theme will allow you to change the colors of some areas, if the Color module is enabled.