Hi,
From your issue description I understand that you want to personalize the display settings so that text should appear darker on the screen.
What is the make and model of your monitor and computer?
We cannot change the Desktop font color. They are dynamic and will show white on dark backgrounds and change to white with a black shadow effect on a light background.
I would suggest you to refer to the below suggestions and check it it helps.
Method 1:
a. Press Windows key +W(It will popup Windows 8 setting charm), **** type Calibrate display color, click in the search box and hit Enter.
b. In Display Color Calibration, click Next to continue.
c. Follow the onscreen instructions and check if it improves the display of your monitor.
Method 2: I would suggest you to refer to the Monitor's user manual and adjust brightness, contrast to different values.
Also refer to this link:
Get the best display on your monitor
http://windows.microsoft.com/en-IN/windows-8/get-best-display-monitor
Hope the above information is useful.