How to force screen to be white, irrespective of tty, DE, etc

I'm trying to create a completely flickerless boot and login with Xorg, and I'm particularly interested in the time between the bootsplash (I use Plymouth) and Xorg being fully loaded (i.e. after the screen flickers black to allow Xorg to start). So far, I have created a Plymouth theme that ends with all-white frames, so I just need to force the screen to go white until my wallpaper (using feh) is fully loaded, at which point I will hopefully be able to seamlessly transition to my desktop. So far, my ideas have included some type of low-level program to force all the screen pixels to be white before and while the tty is loaded, and allow the screen to go back to normal after the wallpaper is loaded, however, I don't know of any program that does that. If there exists such a program, or if there is some method to create one, that would be very helpful. I would probably need to load it as a systemd service in order for it to take effect before the tty is loaded.