Saw that there's no answer to your question and decided to do it :blushing:
So.. open in notepad the file DCPlusPlus.xml, located in Settings directory. Find the line starting with <TextColor
Lets assume that you want to use white text ( this will affect not only the text written in the input box, but the text in transfer view and in favorites and filelist tree view ). You need to change the value to <TextColor type="int">16777215</TextColor>
For black it's 0
For red - 255
We find in Apex source setDefault(TEXT_COLOR, RGB(67, 98, 154)); which is green
It should be RGB, but i don't know why white isn't 255255255 for example.
Or if you want some other values just search for color in that xml, you will find them
Hope that i've helped you
PS: @Crise...it's good one option, or several ones to be added in TEXT_STYLES dialog :)