Cyanobacteria or algae. Once the soil dries, the problem will take care of itself, and both are harmless and not indicative or symptomatic of any problem other than moist soil.

There's no need to get rid of them, which is good because there's no easy way of doing so that won't hurt your new grass.

For seeding, watering two to three times daily is actually a good thing, for short periods to keep the soil and the seed moist. 10 AM and 6-7 PM would be best, with a third slipped in around 3 PM if possible to bridge the afternoon heat--June and July are actually awful times to seed.

For the remainder of the summer, I'm going to suggest slowly backing off watering to daily in the morning for the young grass, then every other day in the morning once temperatures break a bit. Those roots are too young and too small to manage summer weather without what would otherwise be "too much water."

When temperatures tumble, usually around late August to early September for you and I, drop to every third day. Then by late September, every fourth day (rainfall may be taking care of it for you by this time).

Mid October as days get crisp, every fifth day. Late October, every sixth day. November...you can probably skip watering and resume in May next year with the correct once a week, deep watering.

Thank you so much for your helpful information. I think I've been pretty lucky the temperature has been cool for July. I do have some bare patches I think are from the rain washing the seed away so I think I will over seed in September. There are also a lot of weeds coming in so I'm not sure if I should use a weed killer and wait to over seed or wait to apply weed killer until spring?

Hold off until the third mowing of your new lawn before applying any weed killer. That's a complete mowing, not just some tips knocked off here and there, so that could be now, it could be August, it could even be September.

Before that, the grass is really delicate and won't like being sprayed with anything.

You can overseed in mid August just as nighttime temperatures start to drop (strangely, that's happening now but it won't reliably stay that way for a while yet). That gives the new grass plenty of time to develop before winter--but unfortunately you have to go back to watering twice a day minimum on the new seed.

You can ramp it back a lot faster once it's grown in, though, as the weather will be fall-like by the time that happens and water requirements very low.