Well, that script probably can't do it, nor would it work for the menus. It's a useful script to possess nonetheless. If you just want everything that is currently white to be changed to another color though, then the easiest thing to do is to go to the Window_Base script in the editor and find this around line 61 or so:
#--------------------------------------------------------------------------
# * Get Normal Text Color
#--------------------------------------------------------------------------
def normal_color
return Color.new(255, 255, 255, 255)
end
Then just change it to the colour you want. You can experiment with those numbers to get different colours.
black is Color.new (0, 0, 0, 255)