Backs and receivers can wear any number, but if they want to be eligible receivers, they better choose something other than a number in the 50-79 range. NCAA rule 7-3-3:
Eligibility to Touch Legal Pass
ARTICLE 3. Eligibility rules apply during a down when a legal forward pass is thrown. All Team B players are eligible to touch or catch a pass.
When the ball is snapped, the following Team A players are eligible:
a. Each player who is in an end position on his scrimmage line and who is wearing a number other than 50 through 79 (A.R. 7-3-3-I).
b. Each player who is legally positioned as a back wearing a number other than 50 through 79.
c. A player wearing a number other than 50 through 79 in position to receive a hand-to-hand snap from between the snapperÂ’s legs.
Don't have a rule reference for NF, but
AFAIK the rules are pretty much the same.
The thing about reporting comes from the NFL, where that is possible (no such thing in college!!!). However, there are furter differences on the numbering rules between NFL and NCAA/NFHS rules in addition to that one.