LetterAgent
Mail physical letters by just asking your AI assistant.
No, standard faxing is black and white by design, so color originals arrive as shades of gray. A color fax standard exists, but almost no office machines use it, so plan for gray output: darken light colors, avoid red on white for key details, and use bold labels instead of color coding.
Fax was built for phone lines and paper, at a time when color printing was rare in offices. The standard scans each page as black or white dots, with gray shading on better machines, and sends that pattern over a voice phone line. That design kept fax fast and cheap on old phone networks, and it stuck because every machine had to talk to every other machine. A color standard, known as ITU-T T.30 Annex E, was added later, but it never caught on in offices, clinics, or government desks, so two machines that both support color in theory almost never meet in practice.
Online fax services follow the same limit. Even when you upload a color PDF to a fax service, the service converts it to black and white before sending, because the receiving machine expects that format. The result is the same: the recipient gets a gray version, not the color file you uploaded.
Dark colors turn dark gray or black, which usually reads fine. Light colors, such as pale yellow, light pink, or light blue, can wash out to near white and vanish. Red is a special trap: red ink on white paper often faxes as light gray, so red annotations, red stamps, and red "urgent" marks can disappear or turn faint. Green and blue sit in the middle: dark shades survive, light shades fade. If a detail matters, it must survive as black on white, not as a color difference.
Charts and graphs suffer most. A chart that uses color alone to tell lines apart becomes a set of gray lines that look alike. Add labels, line patterns, or direct numbers to each line, so the reader can tell them apart without color. A pie chart with color slices and no labels becomes guesswork in gray, while the same chart with a data table next to it stays usable.
| Original color | Typical fax result | Fix before faxing |
|---|---|---|
| Black on white | Sharp and readable | Keep it, this is the fax ideal |
| Dark blue or dark green | Dark gray, usually readable | Darken it a little if it looks light |
| Red on white | Light gray, often faint or missing | Rewrite the note in black, or bold it |
| Light yellow or light pink | Near white, often lost | Replace with black text or a dark outline |
| Color-coded chart lines | Gray lines that look alike | Add labels, patterns, and a data table |
| Color photo | Gray image, low detail | Raise contrast, or send a scan instead |
Start by printing a black and white copy yourself and reading it as the recipient will. Anything you cannot read in that copy will not magically appear for them. Darken light text, thicken thin lines, and replace color highlights with bold text, underlining, or boxes. For signatures in blue ink, a dark blue pen usually survives, but a light blue pen may fade, so sign in black when a fax is planned.
Raise contrast on photos and shaded areas. A photo with soft shading turns to a flat gray blob by fax, while the same photo with higher contrast keeps edges and shapes visible. Crop the photo tight, so the subject fills the frame, and avoid busy backgrounds that turn to noise in gray. If the photo itself is the evidence, such as a damage photo for an insurance claim, fax is the wrong route: send a scan or a printed color copy by mail instead.
Skip fax when color carries meaning that words cannot replace. Medical images, stained lab slides, color-coded maps, fabric samples, and design proofs all lose their point in gray. In those cases, email a scan, use a secure file link, or mail a color print. A faxed color document that the recipient misreads is worse than a slower color delivery, because the recipient may act on the wrong reading without knowing it.
Also skip fax when the document uses a colored background for security, such as a void pattern or a colored seal. Those patterns are designed to show tampering in color, and in gray they can look like ordinary shading or disappear entirely. Tell the recipient that a color original follows by mail, and fax only a black and white copy marked as a reference copy, not as the original.
No, not to a standard fax machine. Some services advertise color faxing, but that usually means they accept a color upload and deliver a color file to another user of the same service, not to a real fax machine. Once a page crosses to the public fax network, it becomes black and white. If a service promises color delivery to any fax number, ask how the receiving machine displays color, and expect a vague answer, since standard machines do not.
LetterAgent fax is available in testing for US and Canadian fax numbers, with a per-fax quote, page count verified, your approval of the exact total, and a one-time Stripe payment. Like any fax route, it sends in black and white to standard fax machines, so prepare color originals for gray output before you send. For documents where color matters, a mailed color print or a scanned file is the better choice.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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