Computer locks up when watching a video

My Mac mini goes black then I get three beeps in a loop. Seems related to watching videos or playing a browser based game. Apple Store checked RAM which showed okay but maybe not securely in place. Reset and it started normally.

After running at home for a time it crashed again. After unplugged and sitting overnight, it started but with everything tinted purple. Restart gave a normal screen but went black with beeps in a loop again when attempting to watch a video.