It was barely usable. Many developers used the colors of the default theme no matter what. Others used the Windows-supplied colors for the background color and maybe the main foreground color, then used fixed, non-customizable colors for everything else, making everything invisible or hard to see if you used anything but a white-ish background. Trying to use what we now call dark mode was a big no. At best you could replace the wallpaper by an all-black screen so you feel a little less irradiated by your crt.