The red coloration of the document area and the scroll bars appears to be linked to hardware acceleration being enabled. The red color disappears if it is turned off in the settings. I have been dealing with a similar issue as described here: http://support.microsoft.com/kb/939395. Google Chrome is not affected which leads me to conclude it must be a Dragon bug.
Example: http://i.imgur.com/uHiBphq.png
- Win8.1 x64
- GeForce GT620
- all drivers up to date