Which of the following is NOT considered an offense under firearm regulations?

Possessing a valid competency certificate is not considered an offense under firearm regulations because it is a legal requirement for firearm ownership and demonstrates that the individual has met specific standards of training and safety knowledge. This certificate typically indicates that the person is deemed fit to handle and operate firearms according to the law. Therefore, having this certificate aligns with legal regulations rather than violating them, which distinguishes it from the other options listed.

In contrast, offenses such as making a false entry in a required register or selling a firearm without a license are clear violations of firearm laws and can lead to significant legal penalties. Using a colored pen to fill out forms, while unconventional, does not meet the criteria for a serious offense but can reflect poorly on the accuracy and professionalism of the documentation process. However, the validity of possessing a competency certificate is unambiguously recognized in firearm regulation.