This Blue Meanie is a tribute to Heinz Edelmann (https://en.wikipedia.org/wiki/Heinz_Edelmann), the graphic designer responsible for the art direction and character designs in the movie Yellow Submarine:
1) Round, for single-extruder printers. (Change colors when the print is 65% complete.)
2) Square, for single-extruder printers. (Change colors when the print is 65% complete.)
3) Square, for dual-extruder printers. (Load "BlueMeanie-dualstrusion.thing" if you have a Makerbot Replicator 2x, FlashForge Creator or compatible printer.)
June 25, 2016 update: V2 fixes non-manifold surfaces.
If you have one extruder, load the "single print" version and change from black filament to blue anytime after 2mm height (when the lettering starts to print). Or, if you print the "no logo" version, change colors any time after 2mm height.