That is the rainbow effect, a known characteristic of single-chip DLP projectors, and it is not a fault with your unit. It is how the technology draws colour.
A single-chip DLP shows red, green and blue in rapid sequence rather than at once, relying on your eye to blend them. Most of the time it works. But when the eye moves quickly across a high-contrast edge (white credits on black are the classic trigger, subtitles a close second) some viewers catch the sequence as brief red, green and blue fringes. Sensitivity is individual: most people never see it, some see it once and cannot unsee it, and no amount of being told it is normal helps the second group.
Can settings remove it? No. It is the display architecture, and no menu can ask the colour sequence to stop being a sequence. What can help, in decreasing order of usefulness:
The projector itself. Models with faster colour sequencing, or LED and laser light sources that switch colours more quickly, reduce it noticeably. This is a model-specific characteristic, so check the manufacturer's page for the specific unit rather than assuming.
Brightness mode. Lower-brightness modes sometimes reduce the visibility of the fringes.
Seating. Sitting slightly further back reduces how far your eye has to flick across the frame, and the effect is triggered by eye movement.
Content. Bright text on black is the worst case; a film in a dark room with normal scenes may never show it.
If none of that is enough, alternative technologies do not exhibit it at all: three-chip designs and LCD-family projectors show all three colours simultaneously, so there is no sequence to catch. That is the definitive fix, and it is a different projector.
Suspect you are rainbow-sensitive? Tell us before you buy. It decides the shortlist more than almost any other single factor, and finding out after the ceiling mount is drilled is the expensive way to learn it.
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