Here's my take (whether it's right or wrong that's for you to decide). If you mow at 4", it's probably 5-6 inches tall when you cut it. Grass that tall, especially perennial rye, has a longer stalk/sheath than grass that's kept at say 2.5-3 inches. When you cut away 1-2" of grass blade, you are removing the greenest part of the lawn, and revealing more of the sheath, which is generally much lighter. Now when you mowed that path at 2.75, you effectively removed most of the grass blades and some sheath, leaving you with just sheaths, which is why it was brown for a few days after mowing. You also shortened the sheaths compared to the rest of the lawn. The change was the new blades emerging from the newly shortened sheaths. So now the path area has grass with more blade relative to sheath than the rest of the lawn, which is why it's darker green. I suspect that if you mow the whole yard at just 4 inches the darker green path will fade as the grass reverts back to it's longer sheath length. This post was edited by tiemco on Tue, Jun 18, 13 at 13:29

One warning. Do not till. The ground turns to concrete-like crud. Or at least it does around here with heavy clay--I'm not sure where you're located or what grass you're going to use. My advice is appropriate for the clay zone in the northeast and fescue/perennial rye/or Kentucky bluegrass. 'Round these parts, timing would be very late summer to early fall. Cool-season grasses sprout and grow best then and have two full seasons before summer hits. Warm-season grasses differ. A week before you want to seed, make sure you're clear. Use Roundup if necessary. Given there are a lot of weed seeds I'd use a grass-compatible suppressant (Tupersan for cool-season grasses). That can go down with the seed. It sounds like you'd do better with a core aeration to lighten the soil and pull cores to the top. It seems to be a good start around here. Core aerate heavily to give the new lawn something to grow in that's not compressed crud. Seed over the top. Add your Tupersan if desired (and if the grass can deal with it). Add starter fertilizer 'cause the lawn is going to need it. Water thrice daily enough to dampen the seeds but not cause runoff. For fescue/bluegrass, you should see sprouts in 7 to 30 days (the longer being the bluegrasses). For other grasses your mileage will differ. With your location and desired grass we'll be able to give you more specific advice.

As the home appears to be 4 linked structures rather than a single family residence, I'd actually emphasize that feature by choosing different but closely allied colors for all 4 sections. Pick a color for the larger section that you like, and then go to adjacent color strips and slightly up or down the scale for the other three sections. Ocean Pearl for the main larger section. Squirrel for the small section to the left of the main. (going darker emphasises the fact that it's set back from the main house, and that makes it more interesting) Koala Bear for the next. It's a little bit browner, but none of the greys are stark bluish greys. They are all more greiges. And for the last section, darker, and slightly browner again, in Ashwood. Set it all off with crisp white trim and a warm accent color like a brick red/orange or a purplish burgundy for the doors.

lisa-marie, maybe you can help me with my yard. The neighbor's lawns all look better. See what I mean... I don't know whose lawn this is, but I kept the photo for just this occasion. My last lawn I allowed to grow until it stopped growing. For the record, St Augustine seems to stop growing at 32 inches high. I cut it down with a string trimmer to 18 inches and it looked perfectly manicured from a distance. Later I cut it down to 12 inches and later to 9 inches. As long as it is all the same height it looks manicured. As we have probably lectured you time and again, weed n feed is a poor product to use under any circumstances. For your lawn. with no weeds to begin with, it is a total waste of herbicide, not to mention an assault on your soil ecosystem. As I recall you have also pooh-pooh'd the idea of deep and infrequent watering. How often are you watering now?