Answer: Whether your new lawn is sodded or seeded, you can repair bare areas by raking out debris and broadcasting grass seed (the same variety of seed as the rest of the lawn). Fall is a good time to do this. Color variation can be due to over-fertilization, over-watering (or water that puddles in certain spots which can cause fungal growth such as mushrooms), dog spots, or even decaying matter in the soil beneath the lawn. You didn't say how often or with what you've been feeding you lawn, or how often you've been watering or mowing so I can only give you general information. You might want to check with the landscape installers to see what they might recommend.
Good luck with your lawn.
Q&A Library Searching Tips