You are attempting to image a label, signage that was produced by lithography. This method breaks up the original image so that it is comprised of tiny dots of colored ink. Each will have a different dot size and coloring. This type of image is called a half tone.

Now the digital camera images is fabricated using a comparable method. The digital imaging chip in your camera is covered with imaging sites. These brake the image into tiny picture elements (pixels). What happens when you image a half tone via a digital camera is an artifact called a “moire”. This imparts a look of wavy colored artifacts that degrade the digital image.

You can perhaps mitigate the moire by changing the camera to subject distance and by changing the camera angle. However, your best bet is to work with your imaging software to reduce the moire effect. You should also know that if you use a higher pixel count camera with anti-aliasing filter built in, your chance of success will increase. Sorry, this is one of the knotty aspects of digital imaging.