How to make yolks more yellow?

I bought 10 coturnix quail in June, and ended up with 4 hens and 6 roos.  The hens started laying last week, but I'm disappointed in their yolk color.  I'm sure it's because I'm feeding Startena, along with oyster shells.  They need something else in their diet to get the color-  any suggestions?  I don't have a lawn for grass, but can possibly feed some weeds.  I also have a bunch of apple trees, but that's a seasonal treat.  Has anybody tried the omega 3 boosters for chickens?  Any other ideas?

I don't have a lot of choices in gamebird feed-  Purina (which is what I'm feeding) and I think that the feed store might be able to get nutrena for me, but I don't know what the quality of the nutrena is out here for game bird feed.  TSC also has Home Grown, but I think that's just Purina, and it's for older game birds so it's lower protein than the Startena.  

The person I got them from was feeding them organic chicken feed and the lower protein scared me after what I read, but I can go back to that if it won't hurt them.

ETA-  I have chickens, I could mix some of their feed in, would that help?  The chickens are pretty much free range so they get all sorts of other stuff to eat too.  I sell the eggs and I know that my customers like dark yolks.

Well, I offered them kale scraps yesterday when I was giving them to the guinea pigs in the same shed.  So far they looked at them like they were poison.  This is going to be tricky!  I'll try some alfalfa hay, and if they won't eat that, then I'll look for alfalfa meal, or grind up some pellets and mix it into their food....

Do they like to peck at alfalfa blocks?