Next time you fertilize, try using some Milorganite. Milorganite is a very safe, organic, non-burning fertilizer that will really green your grass and feed it at the same time. While it is only 6 percent nitrogen, it has a fair amount of iron in it for greening, and lots of microbes and mircornutrients to feed the soil. While it is recommended to use up to 4 times a year, I found that one application at about 1/4 -1/2 the recommended rate was fabulous and I did not have to fertilize again for 2 years.
Simply put, Milorganite is amazing.