This Bolete stains dark blue immediately when cut or bruised ... or even lightly touched. The underside of this cap is more orange than red, as it is older than in the specimen below.
The Reserve at Rancho Mission Viejo, Orange County, CA.1/16/2016 and 1/19/2015. © Joanne SchwartzFamily: Boletaceae
The underside of the cap is full of bright red tubes where the spores are developed.