"Off colour" is a phrase used to describe something that is inappropriate or offensive. It can also mean that something is not as expected or is unconventional. There are several synonyms for "off colour" that can be used in different contexts. For example, the phrase "offensive" can be used to describe something that is inappropriate or unacceptable. "Inappropriate" is another synonym that can be used to describe something that is not suitable or proper. "Unconventional" is also a synonym for "off colour" and can be used to describe something that is different or unexpected. Other synonyms include "in poor taste," "taboo," and "controversial".