It feels far too soon to be even saying this, but Cartoon Network really had something going with "Redraw Your World" (leading up to the 30th anniversary, no less). It was so vibrant, fresh, and brimming with potential! "Pastel" seems so sterile in comparison.
Non-animation related, but I really dug NBC's "more colorful" rebrand from 2009. That was around the time that I got into Community.
(Also, CapacityTV, the studio that worked on this rebrand, also did the Noods for CN in 2008, so there's some fun trivia.)