We have, at a number of different times, come across situations where it was desirable to use a food safe marker. One example is our custom message hearts project, another is in the course of making circuitry snacks. The topic came up again recently in discussions of Dan Newman’s Nutrition Information and Omelet Recipe eggs, where commenters were debating whether or not one should eat an egg after it has been written on.
There are three types of food safe markers readily available in the US. We tested all three in an Eggbot and just for kicks, by hand on a bit of rolled out fondant.
The primary differences between the markers were in the shades of the red and black, the ink flow rates, and the texture and shape of the nibs. Colors like blue, green and yellow didn’t show significant differences, although it should be noted that the blues in all cases (no matter what color the plastic was) were closer to a sky blue.
Here’s how the logo might look on a printed circuit board, as rendered in gEDA PCB.
We’ve also rendered it in a few sizes and styles– filled or not, and losing the text as the logos get smaller. You can download this set of examples for gEDA 
