Dark eggs are over rated in my opinion. Although I do have welsumers because I love the breed regardless of egg color and I have 3 Penedesencas That I just selected to fill an order out to 25 from Welp. It seems the darker the egg the longer it takes for a chicken to mature to POL. When I was breeding for darker eggs the eggs became progressively smaller down the line. Not saying that will always happen to everyone but it lead me to breeding for qualities that are so much more important.
I just like a colorful egg basket and those nice dark eggs really make it pop! Lol, As far as production I already have more chickens than I need. It's really just a hobby on my part.