# Brown is still brown, forty years on > A wiring loom carries its colour key in the insulation itself, so the documentation survives even after every diagram and label is gone. August 19, 2026 · https://justog.club/stories/wiring-loom-colour-code Eight lengths of wire, each a different colour, cut and set in a vertical key. Brown is PERMANENT LIVE. Blue is HEADLAMP. Red is SIDELIGHT. Purple is PERMANENT ACCESSORY. Green is IGNITION-FED. Light green is INSTRUMENT. Black is EARTH. White is IGNITION. At every cut end, the copper shows. Nothing here is printed. The information is the wire. ## What is this, exactly? A colour code for a wiring loom — the convention that tells an electrician what a wire does by looking at its insulation, not by tracing it back to a label. Eight functions, eight colours, and no words anywhere on the actual loom itself. The lettering beside each length in this design exists for the reader; on the real wire, there's nothing but the colour. ## Why does colour work as documentation at all? Because it can't fall off, fade past reading, or get filed in the wrong folder. A paper diagram tears. A printed label peels, much the way [a windscreen sticker starts lifting at the corner](/stories/oil-change-sticker). A manual goes in a skip when somebody clears out a garage. The insulation on a wire is the wire — there's no separate object to lose, which makes it about the most durable documentation format built into any machine. A fuse box a few inches away still needs its own printed chart for the opposite reason — [a fuse carries an amp rating, not a colour convention](/stories/fuse-box-diagram), so somebody has to write down what it does rather than let the part say it. ## What makes a colour code good rather than just consistent? Consistency across the whole loom, first — every ignition-fed wire in green, everywhere, or the code is worthless. Beyond that, contrast: a green next to a light green only works if somebody can actually tell them apart in poor light, which is why a second wire in that family usually carries a trace of another colour rather than a third shade nobody can distinguish from the first two. ## Can a real manufacturer's actual colour code go on it? The convention itself — colour standing for function — is a method, and belongs to nobody, the same way [a torque sequence is a fact rather than a brand](/stories/mechanic-garage-shirts). A specific manufacturer's exact published code, tied to their part numbers and their diagrams, is a different thing, and licensable the usual way if a real one is the point of the shirt. Eight generic colours against eight generic functions carry the same idea without needing anybody's permission. ## What happens when two electricians don't share a code? They read the loom differently, which is the one real weakness of a system with no words in it. There's no single code every era and every maker has used — green has meant different things in different systems. That's less a flaw than a reason the colour key gets kept, printed or stitched, next to the loom it describes, so the convention travels with the wire even where the convention itself isn't universal. ## Does it work as a gift, or only as a trade shirt? Both. For an electrician, it's their actual working vocabulary printed flat. For anyone who's restored a car with somebody else — a parent, a friend who owns the workshop — it's a fair description of the hours actually spent: mostly bent over a loom, working out which cut end is which by colour, one wire at a time. ## Does it print well? About as well as any print can — this is a chart made entirely of flat colour with hard edges, which is exactly [the kind of artwork fabric printing rewards](/stories/bold-shapes-survive-fabric). No gradients, no fine detail below the weave's floor beyond the lettering, which wants setting a size larger than the real key would carry it. Black as a ground lets all eight wire colours read true rather than shifting against a competing background. This is one of the few designs here where the ink count is the whole point — eight colours, used as data rather than decoration. ## How do I get one made? Describe the loom at [JustOG](/) — which functions to include and how many wires to key. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped. Designs other people have published are in the [shop](/shop). Copper at both ends, and the colour in between says all of it.