Without a better opinion.... I would guess it’s an annual grass, the seeds of which blew in last fall or over the winter. Hopefully as the weather warms it tries to go to seed and with regular mowing it dies out in the process.

Be sure to bag when the seed heads develop and it will go away over a few years. We have a similar one here on the East coast called 'Poa Ana'. Personally, if I had a yard full of that grass i wouldn't really mind it. of course, I know it is only a spring grass but it looks nice until the seed heads form.

No that is some grass that needs cutting

Good point!

Yes, not easy when one has a species of grass invading the lawn and standing out with a strong contrasting color and texture. I have a high quality blue grass lawn that I've needed to target several patches of quackgrass, rather giving the appearance of what you're dealing with, though of much less density. I've carefully spot applied Round Up to the blades, yes time consuming, though effective and now just down to a tiny bit remaining to tackle, otherwise if left to be, the quackgrass would spread itself widely. If indeed an annual grass among your lawn, the problem will soon resolve itself.