Graph colouring remains a central topic in graph theory, providing the mathematical framework for assigning colours to the elements of a graph under specific constraints. In particular, the colouring ...

We regard a graph $G$ as a set $\{1,\ldots,v\}$ together with a nonempty set $E$ of two-element subsets of $\{1,\ldots,v\}$. Let $p = (p_1,\ldots,p_v)$ be an element ...