This is most likely moiré: false color and pattern artifacts that can appear when a fabric’s fine weave conflicts with the camera sensor’s pixel grid.

In post-processing, a targeted moiré reduction tool is usually the best fix. Adobe Camera Raw includes a specific moiré correction tool, and similar controls may exist in Lightroom.

If you don’t have that available, you can sometimes reduce the false colors manually in Photoshop by lowering saturation in the affected color ranges (such as yellow, blue, and purple) using Hue/Saturation or similar adjustments.

Prevention is even better: changing shooting distance, angle, focus slightly, or aperture can sometimes reduce moiré before you take the shot.