2709W, starts displaying full screened colors after about 20 minutes of game

this old monitor i picked up works great, but most of the time, im not using it, so its just the same image for long periods of time. however, when i play a game such as Halo: The Master Chief Collection, after about 20 minutes, it goes to a black screen for a moment, then starts to cycle through different colors. i cant use the menu controls or power button, and my only option is to unplug it. sometimes that doesn't work right away, and doesn't turn on, with only the blue power indicator lit. i couldn't seem to find the setting, or anything online. what do i do? (i use the hdmi port)