Thanks for ypur comment. There are indeed Western red-tails with darker underwing colors. However, some juvenile Westerns appears similar to Easterns. As author Jerry Liguori says under the light morph Western in his Figure RT 07 in "Hawks From Every Angle," "Many Western juveniles have white throat and faintly marked underwing coverts (right), appearing identical to Eastern birds (see FH Pitfall 02)." Unfortunately, GraceG's photos don't show the underwing areas.
Adult red-tails I have photographed in Yellowstone, Southern Arizona, and central Texas have what looks like smeared vertical dark streaks right under the head feathers and lighter looking markings on the belly than what I'm used to with Texas juveniles. Here is an adult red tail from Yellowstone:
And one from Arizona: 