Boletus bicolor

Common Name: None.
Description: Cap 8-28 cm broad, convex to flat in age, dry, perhaps sticky in wet weather, hairless to finely woolly, red to purple-red sometimes stained yellow. Flesh yellow staining blue when bruised but fading again to yellow. Stalk 4-15 cm long, 7-30 mm thick.
Habitat: In small numbers under hardwood, especially oaks.
Edible: Good.

Source: Mushrooms of North America by Orson K. Miller, Jr.