The reason 'Cherry Glow' looks so red is that it
doesn't have the typical white stripped throat common in many
Penstemon (see inset of 'Red Rocks') In 'Cherry Glow' it's
much less white, more muted so the effect from a distance is almost
solid cherry red.
Note, the bloom at left is the exact same bloom as the
top one in the above picture. Just 'moving' back visually
makes it look more red.
And with the magic of computer graphics, we've 'moved
back' again and note, the bloom is getting apparently more solidly
red. That's what makes this one so special. There isn't
a pure solid red Penstemon but don't tell 'Cherry Glow' - she thinks