Abstract: For a given number of colours, s, the guessing number of a graph is the base s logarithm of the size of the largest family of colourings of the vertex set of the graph such that the colour of each vertex can be determined from the colours of the vertices in its neighbourhood. An upper bound for the guessing number of the n-vertex cycle graph Cn is n/2. It is known that the guessing number equals n/2 whenever n is even or s is a perfect square . We show that, for any given integer s ≥ 2, if a is the largest factor of s less than or equal to √s, for suﬃciently large odd n, the guessing number of Cn with s colours is (n−1)/2+logs(a). This answers a question posed by Christoﬁdes and Markstr¨om in 2011 . We also present an explicit protocol which achieves this bound for every n. Linking this to index coding with side information, we deduce that the information defect of Cn with s colours is (n+1)/2−logs(a) for suﬃciently large odd n. Our results are a generalisation of the s = 2 case which was proven in .