[1][3] She specialised in anaerobic digestion as a postgraduate and in 1971 became a postdoctoral fellow for two years at the University of Bristol in the UK.
In 1973 Colleran was elected to the committee of the Galway Association of An Taisce, part of a national voluntary organisation the aims of which were to conservation in Ireland through education, publicity and positive action.
Colleran was among those who were part of an appeal, saying that while the plan for the national park was welcomed by An Taisce, they wanted the visitor centre to be located three or four miles from Mullaghmore.
[16] President Mary Robinson appointed seven new members to her Council of State in February 1991, including Colleran.
[17][18] Other new members appointed at the time were Monica Barnes, Patricia O'Donovan, Quintan Oliver, Rosemarie Smith, Dónal Toolan and D. Kenneth Whitaker.
[20] In 1991, she was one of 15 people appointed to Taoiseach Charles Haughey's Green 2000 Advisory Group, to determine which problems would face the environment in the next century.
[21] She was appointed a member of the National Heritage Council in 1995 by the then Minister for Arts, Culture and the Gaeltacht, Michael D.