Changing the color of your output is relatively simple in NewChk. All the configuration is done at the very start of the chk.php file, shown here.
By changing the $backColor and $keyColor to any CSS acceptable color you can permanetly change the color in newchk.
The $backColor is the color of the main display and is visible in all outputs. It is usually better to make this a darker color to make the Line number stand out.
The $keyColor only shows up in arrays and objects. It works best with a lighter pastel color. This is the color of the associative, property and method names to distinguish the name from the actual values.
For example, if you look at the objects page in the documentation, the $backcolor is blue and the $keycolor is yellow.