DarkAdapted is an interesting solution for adjusting the red, green, or blue color gamma of your display(s). You can set your own brightness settings to fit your needs and those can be easily reverted back to its original state, so other users of your computer also feel comfortable.
The program's installation is quite simple. You download the compressed packed, open it, and install the program by dragging the icon to your Applications folder. During the first run, the program will ask you to either input the serial number or choose which trial mode you'd like to use for the next 10 minutes. The choice is standard for 5 dollars and professional, which is 30 bucks. Professional has quite a few more options than the standard. I suggest you try out the Professional before you buy the software.
The main screen is comprised of the sliders. You get to slide them from 100 to 0 and back to control red or green or blue or all of them in a combination. The main window also has examples of various texts, that allow you to see how they could be read with a specific setting. You can also set predefined presets or create your own.
The developers of the programs included quite a few preferences settings. This way you can make your program behave the way you want it to.
Note: try the professional version right off the bat.