They say a chicken will lay eggs the same color as their earlobes. My six pullets are all red sex-links, so all of my eggs are brown, but if you have different colored birds / eggs you might be able to match them by color.
It's so funny to try to figure out which chicken is laying but I actually saw one of ours lay an egg yesterday. Our Rhode Island Red was in her nesting box and I had the coop door open. She was nose in to the nesting box and I actually say her lay!! Very cool and now I know which egg she is laying. We have a total of 6 chickens and 3 are laying so far. We are getting 3 eggs daily!! Can't wait until they are all laying!