Printed with two PETG filaments on a glass bed with hairspray. Printed the black lines (with a custom end code that doesn’t turns off motors) then printed the white over it in a separate gcode (also with custom start with no homing). It even allows me to go with an exact and cut off hairs and blobs before laying the white. The. The two fuse on the same layer so the color isn’t sticking out.
Interesting technique. For this type of accent work I usually extrude the text into the surface 1-2 layers deep. At that layer I’ll swap filaments, print 2 more, than swap back to my original color. This achieves the same effect in a slightly different way.
I have some Octoprint Pause scripting that will auto park the print head and lock all motors. It will hold the job while you swap filaments. Upon restart it will do a purge in place, rehome XY, then continue its job from its pause coords.
My issue is if it fails you’ve lost your entire print, me if it fails I lost a single layer. Also I like the mirror finish of my first layer.
This is why I have GCode to unfail the print prior to resume. It Rehomes xy so it can pick up right where it left off even if things get moved.