Grasping the (Electric) Crayon

There are quite a few features in the trs80gp emulator, only some of which I’ve worked out how to use. One that did catch my attention a while ago was a peripheral called the Electric Crayon. It happened to have been described in an 80 Microcomputing article at the beginning of 1981 as a box (not huge, not small) hooked up in between a black-and-white TRS-80 and a colour monitor; by issuing commands from your computer (as if sending them to a regular printer, no less) you could generate colour graphics. After noticing the emulator feature I found the magazine again among the issues I brought from my family home, but never quite got around to typing in the demonstration programs.
( A dissertation at length and a program listing )