I believe it's a Carex. Maybe nutsedge.

Yellow or purple nutsedge (the only difference I'm aware of is the flower color).

Pull it as soon as you see it: after just a few leaves, it grows a small tuber (the "nut"), which can sprout a new plant. (The nut is usually left in the soil when the plant is pulled.)

You have a good chance of eradicating it, as you can see the color difference (some can't), and have noticed that it grows more quickly than the grass after a mowing. Keep pulling the lighter, taller bits as soon as you see them.

I got it all out of my backyard, but will never be able to eradicate all the nutsedge in the pasture, so at times more pops up in the back lawn..