Placing the image in certain angles help to start eliminating moire since scanning.

Grayscale images should be placed in the scanner at 15 degree angle. Usually black is printed at 45 degrees.

Color images clear scenes should be placed at 45 degree. It help to preserve Cyan and Magenta that usually have more important information. As you said Yellow is not important, to soft.

Color images dark scenes also 15 degree angle. In this case black is more important than cyan and magenta.

Another important point is that image should be scanned at maximum optical resolution available in the scanner. This soft the scan. Printed images are to sharp. Also, Unsharp Mask should be avoided.

Regards