Spending a lot of time in front of a bright LCD monitor can be a real pain for the eyes. But there’s no good reason why you should keep the default white background behind your code. After a search I found that some people have already prepared configurations that will allow you to have bright text on a dark background.

Quick list of themes

fb-zenburnishhttp://www.noiseandheat.com/blog/
Dark theme for Flash Builder 4http://www.likidu.com/blog/
The Typography of My Flash Builder http://kevinsuttle.com/

After testing them for a while I’m currently using fb-zenburnish.

Installing a theme

First download the file, and unzip if necessary. You should have an .epf file. Now go to the Flash Builder, and from the File menu select Import->Other. (you might want to backup your current settings before importing the new ones, just choose Export instead of Import and it should be a straight forward process)
Import -> Other
Than choose Preferences from the General node and click Next.
Preferences
Than just browse for the epf file and click Finish.

Your brand new color scheme should be set.