They look like two different forms of Phalaris arundinacea, AKA Gardener's Garters or Ribbon Grass.

The plain green copy is the straight species, and the variegated one is either P.a.var.picta 'Picta' or P.a.var. picta 'Feesey.' The difference between the two variegated cultivars is a slight pink tinge in the leaves on 'Feesey,' most noticeable in the spring.

They are both considered to be invasive in certain areas, like the Midwest.

The foliage will turn brown by late summer, but if you cut them back to within 6" of the ground, they'll throw up fresh new foliage through the fall.

Thanks so much for the info!