Agaricus campestris - Thin, velvety whitish cap (with some grassy sticking to it) with deep gills (not touching the stem) changing from bubble gum pink to dark chocolate with age. Thin almost straight stem with a slight taper to the bottom. Good mushroomy odor.
Growing in the grass nearby some Colorado blue spruce, ponderosa pine, white pine. Definitely in the grass area, not in the dirt or drip zone of the pines.