I started using my child's washable crayola markers, because she kept breaking the lead out of my dang pencils. It works great too. I keep whatever color marker the chickens are in their coop and can mark the eggs as I collect them and don't have mix ups.
well it seems as if there are may options lol i will probably use what ever is closest to me who knows what it will be it might even be a eye liner pencil lol