[mossthatcher]

The shiny back of the blade makes me think annual ryegrass.
This video might help

I have some in my back garden because I was messing around trying all sorts of choices on the shelf.
Canada Green hydro seed was fun to use but the dye didn't stay blue long enough.

Which Scott's bag were you using?
They have a cheap contractor mix which it might have come from.
The other ones like quick n thick, tough, awesome etc are less likely to have caused it.
My neighbour just used the blue one in autumn and it came up great.


Hand pulling is your only real option as there aren't any selective herbicides.