Red urchins are found in lower rocky habitats intertidally compared to purple urchins.  From very low intertidally to about 90m is where you might find one of these prickley guys.  The lower they are the closer they are to Macrocystis pyrifera.  They also have tendencies to gather little rocks and shells to cover themselves while exposed to air.   They range from Northern Japan and Alaska to Isla Cedros, Baja, California.