Lawns

It's getting to be the time of the year in the Midwest that the lawns are finally coming around. Just looking for a little advice. I'm pretty anal about my yard but after moving into a new house about a year and a half ago, I am still fighting my yard. My front yard was sodded by the builder and the back was seeded. Of course the builder used different types of grass between the seed and sod, so now that the seeded yard is coming around, it's a bright green where my front yard is a darker, deep green. Is there anyway to fix this other than continual overseed year after year?

Also, my lawn seems to come around a little slower than others. It takes to almost June to be thick like others. Currently I'm using the 4 seasons of fertilizers from Scotts, the TurfBuilder series. I know there is better stuff out there, but what do you guys recommend? I am unsure of the actual grass variety as I did not put it in. The front is a smaller blade, while the back is a thicker blade.