This is the giveaway! The stem is usually yellow but heavily "flushed" or streaked with bright red or reddish-brown.
Use a local field guide like the Field Guide to Mushrooms of Western North America or join a local mycological society to learn from experienced foragers. Fungi – the 'good' and the 'bad' - A Rocha Canada boletus zelleri
The Zeller’s Bolete is often described as "regal" because of its deep color palette. Look for these key features: This is the giveaway
While Zeller’s is fairly easy to identify, never eat a wild mushroom unless you are of its identity. as these are often toxic.
A good rule of thumb for bolete beginners is to avoid any species with red or orange pores , as these are often toxic.