Here is a look at understanding TCU’s 4-2-5 base coverages. An important thing to note, TCU plays a lot of split field coverages, and may run any of these concepts in conjunction with another.
Cover Blue: It’s better known as 2-read/palms coverage. It is a blend of quarters and cover 2.
Cover 5: It’s a 2 deep, 5 under pattern matching zone coverage.
Cover 2: It’s an inverted cover 2, with the free safety looking to rob any deep in-breaking route by #1 to the field side. If the ball is between the hashes, he will look to rob #1 to the strong side of the formation.
This is a 2 hour clinic video, and it details the fronts, alignments, and coverage rules used by TCU.