The selection box that appears when you hold the left mouse-button and drag your mouse away is blue by default on all versions of Windows. However you can change this setting by using two registry values in Windows 7 and Windows 8.
Open the registry by typing regedit into the Windows 7 menu search on Windows 7 or by right-clicking the bottom left corner on Windows 8 and opening a Run... prompt. Enter regedit into it.
- In the registry you will see a tree structure on the left pane - in it, browse for Computer\HKEY_CURRENT_USER\Control Panel\Colors and click it once.
- On the right pane, look for the value of HotTrackingColor. It is given in three values representing the ratios of red, green and blue that range from 0 to 255. Enter values that mix to the color you want to have (you can check the color values in a graphic editor).
- Do the same for he value of Hilight.
These two values also alter the color of hyperlinks and the color of highlighted text. After you set the values, close the registry and reboot your machine. Afterwards the selection box should have the color you chose.
The two different values each stand for a different part of the box - the first determines the color of the inner transparent space, the second determines the color of the non-transparent border. This means you can have different colors for each.