The short answer is that they can lay eggs in the AM, they can lay eggs in the PM, and that can change. Perfectly normal.
Now the long answer. It takes about 25 hours for an egg to got through the hen's internal egg making factory from when the yolk is released until the egg is in the nest. About 25 hours dos not mean you can set your watch by it. For some hens that can be less than 24 hours, for some it can be over 26. Some hens lay about the same time each day, some gradually get later each day, with others it can be scattered.
There are different signals that tell a hen when to release a yolk to start that process. One signal is that she lays an egg. Typically about 20 minutes after a hen lays an egg she releases the next yolk. Again, about does not mean exactly. Light also plays a part in releasing that yolk. The hen doesn't need to be laying an egg in the dark so daylight is a trigger in releasing that yolk so she doesn't need to lay in the dark. A typical pattern is that a hen will lay an egg a day with each egg getting later until she runs out of daylight, then she skips a day, starts laying in the morning, and repeats the cycle. Each hen is different. Not every hen lays an egg a day, some lay every other day or on some other schedule. Most of those will probably be in the morning.
Sometimes something can happen that causes a hen to pop an egg out early or maybe delay laying it for a while, usually some kind of stress. This can sometimes lead to strange looking eggs as well as strange schedules.
The color of the yolk has nothing to do with nutritional value. That color comes from what they eat, I think different carotenes, not just beta-carotene. Some dark green plants can provide that "dye" to make darker yolks. Some Layer feed has marigold petals in it to color the yolks. While it doesn't affect nutritional value I think dark orange yolks look better.
Taste is pretty subjective. Some people can tell tiny nuances in flavor, many of us can't. How you cook them can make a big difference in being able to taste differences. I think what they eat can make a difference in taste but it is probably pretty subtle in most cases. We all have different taste buds, what I like you might not. So I suggest trial and error. Feed them something for a couple of weeks if they will eat it and see if you can tell a difference. Then try something else. Maybe grow basil, oregano, sage, and rosemary and see what you think. Or try other things. Experiment for yourself and see if you think it is worth it.