Hens and their eggs can at times be easy to identify if you pay attention to your hens and get to know them. Many eggs do look alike and it can be hard to tell who laid what. There are differences in egg colors according to the breed but some can be so subtle you'd be guessing at best.
What breed of hens do you have? Brown egg layers? White egg layers? I can tell my Marans and BR eggs from my BO's and RIR's but unless I see the other Rocks/Wyandottes/Brahma crosses actually laying the rest is a mystery.
The link Katy gave you is an excellent resource.
