I have seen a red screen on my wiiU controller yes and on the TV the wiiU logo and it installed correctly now whatThere's an edit post button.
Don't go into Wii mode when running wupserver. Go into Wii mode after running writedol.py and replugging the Wii U.
You should see a red screen when booting into the wupserver fw.img. Do you see that red screen when booting in?
I can post a video showing what it looks like when booting into the fw.img, if you're not sure.