Appreciate the prompt response.
Have you checked other channels if the same red tint issue occurs? If you noticed that it's only happening in Plex, we suggest you try removing the channel and then reinstalling it.
To ensure the process is successful, restart your device before adding the channel back in. We would recommend doing this from the Settings menu by navigating to Settings > System > Power (If you do not see a Power submenu, skip to the next step.) > System restart.
Keep us posted!
All the best,
Roku Forum Moderator