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Home > Guides > Faxing in colour
No, standard faxing is black and white only: a colour page sent by fax arrives as a black-and-white image, with colours converted to shades of grey. Colour highlights, red ink, and colour-coded charts lose their meaning in that conversion, so for documents where colour carries information, use a scan, a photo, or a printed copy instead.
A fax scanner reads each page as light and dark, not as colour. Dark colours become black or dark grey, light colours become light grey or white, and colours of similar brightness become the same grey even when they look very different on screen. Red ink on white paper, for example, often comes out as a medium grey that is harder to read than black ink, and yellow highlighter frequently vanishes entirely. The receiving machine prints the grey-scale image, so the recipient never sees the original colours.
This is a property of the fax standard itself, not a setting you can change. Fax machines were designed for text documents on phone lines, and the standard defines black-and-white transmission. Some modern fax services accept colour scans as input, but they still convert them to black and white before transmission, because the receiving fax machine can only print in black and white. A colour fax number does not exist in the standard sense: any number that receives faxes receives them in black and white.
| Original colour | What the recipient sees | Risk |
|---|---|---|
| Black ink | Black, clear | None |
| Dark blue ink | Dark grey, usually readable | Low |
| Red ink | Medium grey, harder to read | Missed words or numbers |
| Yellow highlighter | Often invisible | Emphasis lost entirely |
| Colour chart with legend | Greys that may look alike | Legend becomes meaningless |
First, redesign the document for black and white: replace colour coding with labels, patterns, or different line styles, and write out what the colours meant. A chart that uses solid, dashed, and dotted lines with a printed legend survives faxing, while a chart that relies on red versus green does not. For forms, replace coloured sections with bold headings and boxed areas, and avoid asking the recipient to sign in blue or check the red box.
Second, choose a different channel when colour is the information itself: a medical image with colour annotations, a design proof, or a photo where colour shows a condition should go by secure email, a portal upload, or a printed copy by mail, not by fax. If you must fax a colour original, add a typed note explaining what the colours meant, and confirm with the recipient that the grey-scale version is sufficient for their purpose. Never assume the recipient can reconstruct the colours from the fax.
The same limit applies: LetterAgent faxing sends to US and Canadian fax numbers, and the receiving machine prints in black and white. You ask your AI assistant, get a per-fax quote with the page count verified, approve the exact total, and pay once through Stripe. Fax is currently in testing, so it is described as available in testing and a fax is never promised to send on a particular day. Before approving a fax of a colour document, check whether any colour carries meaning, and if it does, rework the document or choose another channel.
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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