NCAA Football Rules page 16
i. White field yard-line numbers not larger than 6 feet in height and 4 feet in width, with the tops of the numbers nine yards from the sidelines, are recommended.
j. White directional arrows next to the field numbers (except the 50) indicating the direction toward the nearest goal line are recommended. The arrow is a triangle with an 18-inch base and two sides that are 36 inches each.
k. The two hash marks are 60 feet from the sidelines. Hash marks and short yard-line extensions shall measure 24 inches in length.
l. Nine-yard marks 12 inches in length, every 10 yards, shall be located nine yards from the sidelines. They are not required if the field is numbered according to Rule 1-2-1-i.