Surprise black eggs after switching their bedding to shredded paper

About 3 weeks ago I swapped the pine shavings in the coop for shredded office paper since I got a massive box from a friend who works at a law firm in Columbus. I figured it would be fine but the very next morning one of my barred rocks laid an egg with a weird dark speckled shell, almost looked like someone dotted it with a marker. Then two days later another hen produced a fully charcoal colored egg and I panicked thinking something was wrong with them or they got into something toxic. Turns out the paper has some ink residue and the hens were pecking at it, which messed with their pigment glands temporarily. I called my vet and she laughed and said it's harmless but now I'm stuck with a dozen eggs that look like they belong in a goth bakery. Has anyone else had odd shell colors show up from changing bedding or litter in the run? Should I just go back to shavings or is this a fun quirk to keep around for a while?