An (n + 1)-coloured graph $\left(\Gamma,\gamma\right)$ is said to
be $m-bipartite$ if m is the maximum integer so that every m-residue
of $\left(\Gamma,\gamma\right)$ (i.e. every connected subgraph whose
edges are coloured by only m colours) is bipartite; obviously, every
(n + 1)-coloured graph, with n $\geq$ 2, results to be m-bipartite
for some m, with 2 $\leq$ m $\leq$ n + 1. In this paper, a numerical
$code$ of length (2n \textminus{} m + 1) $\times$ q is assigned
to each m-bipartite (n + 1)-coloured graph of order 2q. Then, it is
proved that$any\; two\; such\; graphs\; have\; the\; same\; code\; if\; and\; only\; if\; they\; are\; colour-isomorphic$,
i.e. if a graph isomorphism exists, which transforms the graphs one
into the other, up to permutation of the edge-colouring. More precisely,
if H is a given group of permutations on the colour set, we face the
problem of algorithmically recognizing H-isomorphic coloured graphs
by means of a suitable defi{}nition of H-code.
