It's a rectangular grid. People aren't going to troll with dicks, but swastikas.
[1] https://www.oled-info.com/gs5-diamond-pixel-architecture-not...
W-OLED and QD-OLED have unconventional layouts compared to LCDs but every pixel has the complete set of sub pixels (RGB for QD-OLED, RGBW for W-OLED) so it looks more like this:
https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...
Just mentioning as while AMOLED phones being the majority of OLED displays seems plausible to me, it's likely not what people in this thread are picturing when they see OLED.
Honourable mentions go to the TARDIS picture at https://mstdn.ca/@Chigaze/112683847369819438 and the Sierpiński gasket attempt at https://mastodon.online/@Zotmeister/112684295968651688 .