"Blue-on-blue" is a term that is used to describe accidental friendly fire incidents. However, there are plenty of synonyms that can be used to convey the same meaning. Examples of such synonyms include "friendly fire," "friendly fire incident," "fratricide," and "friendly fire accident." Additionally, depending on the context, "blue-on-blue" could also be replaced with other terms such as "self-inflicted harm" or "unintentional harm." It is important to note that the use of such synonyms depends on the context in which they are used.