We're so used to the typical combination of black text/white background in our office apps that we're practically blind to it. Yet, the simple act of switching these two variables could be the key to keeping headaches, eye-strain and tiredness at bay -- or alleviating them completely.
OK, so it's not a miracle cure, but I can say first-hand that swapping Visual Studio's default white/blue/black colour scheme to the soft and enchanting shades of Son of Obsidian (see above) has done me wonders. I'm just that little more productive, and when you're a lone developer, any bonus time you can collect is heavenly.
Of course, switching colour schemes applies to many other programs and operating systems. You don't have to go all-out like I have -- you can just flip the foreground and background colours of your favourite app and go from there.
If you do get the colour bug, hit up Studio Styles. Its sole focus is on colour schemes for Visual Studio, but there's nothing stopping you from using it as a template gallery and manually applying schemes to whatever programs you use.