Colleran later attended University College Galway (UCG) where his academic life was augmented by further success on the football field. In 1962 UCG reached the final of the Sigerson Cup, an All-Ireland inter-varsities competition for third level institutions. University College Dublin (UCD) provided the opposition on that occasion as Colleran made one of his first appearances at Croke Park, which UCD narrowly won by 3–7 to 2–7. UCG contested a second consecutive Sigerson Cup final in 1963, this time with University College Cork (UCC) providing the opposition. On this occasion Colleran ended up on the winning side by 1–9 to 1–3 and collected an inter-varsities winners' medal. A third successive Sigerson Cup final appearance beckoned for Colleran and UCG in 1964. A 2–10 to 0–5 win gave UCG the title and gave Colleran a second Sigerson Cup winners’ medal.