Red or blue lettering can develop soft color edges in a JPEG even when its quality setting is high. One possible cause is chroma subsampling, which stores color detail at a lower spatial resolution than brightness detail. Compare an equal-size lossless export and inspect the actual JPEG; raising the quality slider alone may not change its sampling mode.
Confirm that the damage is in the file
Download the published image and open it at 100 percent. Browser scaling, a messaging-app preview and a screenshot can each change the apparent edge. Compare the text in the editor, the local JPEG and the downloaded delivery using the same pixel dimensions.
Check black lettering as well as red lettering. If only colored edges spread while the dark structure remains clearer, reduced color resolution is a plausible explanation. If every edge is equally soft, investigate resizing, source resolution or compression more generally. These observations are clues, not a way to infer an exact encoding parameter without file inspection.
Use a small comparison strip
Create a duplicate containing the affected red word, a dark version of that word and a representative photograph area. Export the strip at identical dimensions as JPEG and full-color PNG. Do not enlarge one version or add sharpening to only one; that would introduce a second variable.
MDN explains chroma subsampling as part of image encoding. Some encoders expose full-color sampling controls, while others select them automatically. Where a supported encoder offers a choice, test a full-chroma export against its default. Verify the saved file rather than assuming that a number such as quality 100 means all color samples are preserved.
A hypothetical exhibition tile
Imagine a square tile with a small crimson event date over pale photographic artwork. The PNG keeps the letter boundaries readable, while one JPEG introduces a red fringe outside the strokes. A black-date comparison remains clearer. The designer chooses the lossless delivery for this destination after checking its file-size requirements.
This is an illustrative test design, not a measured encoder comparison. If the receiving platform converts the PNG to another format, check the final downloaded asset there as well. A clean local export does not guarantee a clean platform derivative.
Improve the layout before forcing the encoding
Keep important names and dates as editable text in an external layout or as accessible page text where appropriate. An Imagild image can supply the artwork, while verified lettering is added afterward. Generating the entire image again is unnecessary when the problem begins during export.
Slightly larger text, stronger brightness contrast and less extreme tiny saturated lettering can improve practical readability. Make those choices against the real final dimensions, not an enlarged design canvas. A lossless format cannot recover text that was already blurred in the source.
Acceptance boundary
Approve the exact delivered file when the date is readable at its intended size and no distracting color fringe appears in the chosen viewer. Preserve the artwork master and separate typography so another export does not require repainting. Distinguish a one-export sampling issue from cumulative JPEG damage caused by repeatedly saving intermediate copies.