Actually my issue is the same as decribed by @shadowbob in another thread.
No solution is posted for color problem.
I tried 2 vga boxes, different cables, and I used my laptops via output. The issue still occurs. As you can see in the image below. (the screen has green color all over it)
“Has anyone else has issues with RGBHV input and the Dreamcast? Not sure if something has started failing in my unit, but the other day I noticed that there is a random flicker/white level change happening with VGA input from my Dreamcast. Noticeable on primarily lighter colors, especially the boot sequence. None of the other inputs have this occur or even with RGBS over AV3. Tried swapping Dreamcast systems, power supplies for the OSSC and it still happens. Bypassing the OSSC doesn’t show this issues on my VGA monitor. I’m going to try another RGBHV source like my GCN or my Xbox 360 VGA cable tonight to see if it’s that or something weird with how my Dreamcast VGA box interacts with the OSSC.”