I used a public domain biohazard SVG symbol to design a biohazard sign to mount on a door. The size is scaled such that it exactly fits the 18x18mm print bed of the Prusa Mini.

I printed it in Prusament PETG splitting the lower 2mm backplate in orange color and the upper 2mm sign in galaxy black color. This can be done easily by slicing in Prusa slicer, switching to the middle layer where the sign begins using the vertical slider on the right and pressing the small + next to the slider to add a filament change to the gcode.