I've been trying to come to a clearer/more precise understanding of the rules of heraldry and the resources I've been looking to for information have been vague on a few specifics of the rule of tincture (i.e. avoiding metal on metal / colour on colour). From what I've found, said rule:
- Does not apply between divisions of the field (ex. Quarterly Azure and Gules is fine)
- Does not apply to furs
- Does not apply to charges that lie partially atop more than one division of a divided field
- Does not apply to charges depicted proper
However, I haven't been able to find something definitive stating for certain whether the rule of tincture applies to variations of the field (wherein said variations consist of tinctures rather than something depicted proper). For example, would 'Barry of eight Sable and Gules' be in violation of the rule of tincture, or is this another situation that is excepted from it? Some sources I've looked at have considered some patterns to be both variations of and divisions of the field, such as gyrony, further confusing the issue.
Additionally and regardless of how the tinctures comprising a variation of the field are considered under said rule, is the rule of tincture considered to apply to charges overlaying a variation of the field, or not?
I'm aware that there are certainly existing examples of arms that don't follow the rule of tincture (and am unsure as to what extent the prevalence of said rule extends across different European heraldic traditions), but would still like to have a more precise knowledge of its extent in certain cases such as this.