  In an improper colouring an edge $uv$ for which, $c(u)=c(v)$ is called a
\emph{bad edge}. The notion of the \emph{chromatic completion number} of a
graph $G$ denoted by $\zeta(G),$ is the maximum number of edges over all
chromatic colourings that can be added to $G$ without adding a bad edge. We
introduce stability of a graph in respect of chromatic completion. We prove
that the set of chromatic completion edges denoted by $E_\chi(G),$ which
corresponds to $\zeta(G)$ is unique if and only if $G$ is stable in respect of
chromatic completion. Thereafter, chromatic completion and stability is
discussed in respect of Johan colouring. The difficulty of studying chromatic
completion with regards to graph operations is shown by presenting results for
two elementary graph operations.
