The nitrogen will definitely turn it green. You'll have to water it quite a bit for it to be really effective, but it does work wonders.
If you're worried about disease, I would recommend spraying your lawn first with
Spectracide Immunox. After spraying, wait until the lawn dries completely and then spread the nitrogen. After the nitrogen, give it a good watering so it gets down into the soil.
the Immunox just needs to dry on the lawn. Once dried, it won't wash off with the watering. If you catch it early in the day, you can probably have it all done in a single day.
I'm far from being any kind of expert, but this has worked for me in the past.
Randy