Up to now I had ony connected my OPI to the livingroom TV, surprisingly enough. Since this is not always convenient I hooked it up to my computer monitor upstairs. Sine that monitor doesn't have an HDMI input I had to dig around a bit to find an HDMI to DVI cable, which I eventually found. So I connected my OPI to the monitor and I got a purple screen. After booting up my desktop was glowing in all kinds of purple hues. Thinking that maybe a second OPI had fallen victim to me I quickly tested it on the TV downstairs. It was fine... Must be the cable then... I connected a Raspberry PI and that one was giving a normal, clear picture on the monitor. Hey welcome to the wonderful world of the Orange PI, where every seemingly trivial task presents you with a challenge to keep you occupied for at least several hours! I guess it's back to Googling and digging around the forums to get this fixed..
UPDATE: And indeed after going through the forum there is indeed a thread describing issues with HDMI to DVI. So I gave the suggested solution a try and now I have a proper display :)