"ATWT" was the last place I remember hearing that phrase.
The announcer at the time was Dan Region and, IIRC, the
announcement was discontinued after Procter & Gamble let
him go in 1998.
Re "Stay tuned for 'Dark Shadows,' next in color...": ABC was
big on that phrase "in color" in 1966 and '67. They dropped
their opening of three circles lining up to form abc in
different colors starting with "Batman" in order to put in an
extra commercial minute; eventually, there'd be either a slide
of the show's logo with the words "in color" underneath, an
announcer (such as Bob Warren on "The Lawrence Welk Show"
or Hank Simms on the Quinn Martin shows) intoning the phrase
"in color," or one of the network's big stars such as Elizabeth
Montgomery saying the phrase; she'd appear at the start of
"Bewitched" and say, "Hi! Stay tuned for 'Bewitched'...
next...in color."