<s>
In	O
graph	O
theory	O
and	O
theoretical	O
computer	O
science	O
,	O
the	O
colour	B-Algorithm
refinement	I-Algorithm
algorithm	I-Algorithm
also	O
known	O
as	O
the	O
naive	O
vertex	O
classification	O
,	O
or	O
the	O
1-dimensional	O
version	O
of	O
the	O
Weisfeiler-Leman	B-Algorithm
algorithm	I-Algorithm
,	O
is	O
a	O
routine	O
used	O
for	O
testing	O
whether	O
two	O
graphs	O
are	O
isomorphic	O
or	O
not	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
the	O
new	O
color	O
of	O
the	O
vertex	O
is	O
the	O
pair	O
formed	O
from	O
the	O
previous	O
color	O
and	O
the	O
multiset	B-Language
of	O
the	O
colors	O
of	O
its	O
neighbors	O
.	O
</s>
