An understandable thought, and we all have to learn things.The three that say Fertilized are darker than the one that doesn't say it, sorry.
I have never cracked open a fertile egg before, so I thought wrong.
Good observation with the yolks by the way.
-The Angry Hen
A lot of times photos like these use commercial eggs for the not fertile since those come from laing houses with no roosters present. ...the difference in feed/management between those birds and the flock the fertile eggs are from account for the difference in yolk color