Genetics also plays a big role in leg color, along with a healthy diet. I used to feed my birds Purina, but switched to a "lesser quality" feed a few months ago... DuMOR. I supplement this with Purina Scratch Grains. The picture below is of my 14 week old RC red, and it's been eating DuMOR 24% and Scratch Grains since day 1, with occasional vegetable supplements. I haven't found any mention of Marigold in DuMOR chick feed, but as you can see, this chick has some bright yellow legs...The feed I use promises both marigold extract and added calcium for shell strength. I have used the feed for several months before deciding to offer my own supplements mixed into it. I saw no real results in shank color or yolk color until using the supplement. The one girl I got from Marcia had very pale shanks when I got her, but she was already a year old so not much I could do with it. I did see a but of improvement on the leg color while using the supplement, but what was done was done. When they get to a certain age they're already developed and not much can be done...
Theres probably a bit of marigold extract in their, but to be honest, nothing to do any difference. Its Purina, not one of my favorite brands but the only thing we have here.
My cockerels are slowly starting to fill out but I wanted to help speed up the process a little, so today I made a run to TSC. I bought 50lbs of DuMOR 24%, 50lbs of Purina Scratch Grains, 40lbs of BOSS, 10lbs of Manna Pro Poultry Conditioner, and 30oz of freeze dried mealworms. I mixed the Poultry Conditioner with 20lbs of Scratch Grains (can go up to 50/50). I found out they love the conditioner pellets, and are absolutely crazy over mealworms. Mealworms aren't cheap, but with 50% protein, it doesn't take much...