i have used grass clippings but i know someone who does use newspaper but i would think some of the colored boxes might have a wax or plastic coating which wont decompose

I have used newspaper, landscape fabric and mulch. I did not used newspaper with color because I was using it in a flower bed and had heard not to use color due to the dye used to make the color. I have had the best results with landscape fabric covered with hardwood mulch. You have to overlap each piece of newspaper or fabric because weeds will find any gaps anywhere. Hope this helps.

Newspaper works well in gardening if dipped in water and overlapped to form a paper mache cover. I then use pine straw over that. The newspaper decomposes over a season so it's not a permanent cover. Some printers use only vegetable inks now. You would have to check with your newspaper to be sure. I would not use heavier materials like boxes.