This theme has blues and browns - it is really easy on my eyes.
https://addons.mozilla.org/en-US/firefox/addon/3663

I also use my nvidia video card driver/program to adjust the whole monitor settings to my preference.
If you can find out the video driver you have there might be an enhanced download you can get that will do the same as the nvidia

Have you also tried your monitor adjustment buttons to see if you can adjust it to comfortable levels?
http://owlcroft.com/monfix.shtml

you can also fine tune colors and choices in your control panel/ display /appearance/advanced button
you just click on the part you want to change and then try different colors , font sizes ect.

Other Firefox add ons-

Noscript - asks you if you want to allow scripts or not most of the time it's not needed to view the pages in question and if it is then you can decide how much to allow.

WOT{web of trust} puts a little safety rating icon on sites or search results lists.
those software download sites have about 40% orange and red warnings - greens mean safe and orange/red means bad.