I have a cool season mix of turf grasses and there are a few areas that don't look like the others that I need help identifying so that I can select the correct mode of action to remove the trouble areas. The areas seem to be darker blue than the surrounding area and I typically notice them because of the presence of the higher concentration of dead stalks. The area has a shallow root system and I have pulled a few small areas up as shown by the bare spot in one of the picture. I have also attached a few pictures of individual plants that I pulled from the area.
Denver County Colorado
I can't give you a definitive ID of your grass but I'm pretty sure it is a Kentucky Bluegrass based on the boat-shaped leaf tip. To get a better ID, I'd have to examine an inflorescence and look at the spikelets.
There are different species and cultivars of bluegrass, so that could account for the color variation you've observed and I detect signs of some fungus which might explain a little dieback. However, you say it "has a shallow-root system" and that might be a big clue: it raises the possibility of beetle grubs feeding on the roots and that would definitely explain the dieback. Here are a couple of CSU Extension fact sheets that you can use to figure that out: