After reviewing all the descriptions on record, the specimens with a brown to blackish cap are suspected to be Phylloporus arenicola. Red caps are Phylloporus rhodoxanthus. The original description of Phylloporus arenicola by Smith and Trappe (Mycologia 64: 1138-1153) says non-bluing and this has led to confusion over the northern California species. After making at least 10 collections, it is accurate to say the bluing is slow, slight and fades within minutes to yellow again. But the gills do blue when bruised in fresh specimens.