How color matching works
Filament Select does not compare colors the way a computer stores them. It compares them the way an eye sees them.
The problem with RGB distance
The obvious way to find the closest filament is to treat each color as a point with red, green and blue coordinates, then pick whichever spool is nearest. It is one line of code, and it is wrong in a way that is easy to feel and hard to explain.
RGB is a storage format, not a model of vision. Equal steps in it are not equal steps in perception. Human vision is far more sensitive to changes in green than in blue, so two dark blues separated by a large RGB distance can be indistinguishable, while two greens separated by a small one look obviously different. A matcher built on RGB distance confidently returns the wrong spool and gives no hint that it has done so.
Matching in a perceptual color space
Our matching model evaluates every color in a perceptual color space — CIELAB, the international standard built so that distance between two colors tracks how different they actually look, rather than how different their stored values happen to be.
Within that space, colors are ranked using a perceptual color-difference calculation called Delta E, in its modern CIEDE2000 form. It is the same family of measurement used for quality control in commercial printing and paint matching, and it corrects the places where plain distance still misbehaves: near-neutral colors, the blue region, and pairs that are very light or very dark.
Every filament color in the catalog is normalized into the same space before anything is compared, so a spool measured from a physical print and one published by a manufacturer are ranked on the same footing. The result is a single number per candidate: how different this spool looks from the color you asked for. Lower is closer.
What a ΔE number means
- Below 1.0 — not distinguishable by a trained observer under controlled light.
- 1 to 2 — distinguishable only in side-by-side comparison. For a printed part, effectively the same color.
- 2 to 5 — a close match. Noticeable if you hold the two next to each other, fine in isolation.
- 5 to 10 — clearly the same family, clearly not the same color.
- Above 10 — related, but nobody would call it a match.
The pairs below show why the metric matters. The second number is the straight-line distance an unweighted comparison would give — notice how differently it ranks pairs that your eye has no trouble separating.
Two navies most people cannot tell apart
ΔE 1.70 · straight-line distance 3.56
Two greens that read as clearly different
ΔE 8.14 · straight-line distance 14.75
Two reds within a shade of each other
ΔE 3.65 · straight-line distance 5.94
Why the ranking is trustworthy
A match is only as good as the color data behind it, so the catalog records where every value came from — measured from a physical print, published by the manufacturer, sampled from an official product image, or estimated — and measured values take priority. Filament pages say which one they are rather than presenting a guess as a measurement.
Ranking is by measured color difference and nothing else. Affiliate relationships play no part in it: a spool with no purchase link at all will outrank one that has a link if it is the closer color.
What the numbers cannot tell you
A ΔE of 1.2 is a statement about two color values, not a promise about two spools. Filament color shifts with pigment batch, layer height, infill showing through thin walls, print temperature, and whether the surface is matte or silk — a silk finish in particular reads several units lighter under direct light than its flat value suggests.
Treat a close match as a strong recommendation, not a guarantee, and order a sample before committing a large print to it.