Colless was born in
Tamworth to Kenneth Hargrave Colless and Yvonne Tipling and was raised on a rural property at
Bundarra, near
Inverell. He undertook primary school by correspondence from the Blackfriars Correspondence School in Sydney; and secondary education at Tamworth and
Singleton High Schools. Colless won a cadetship with the Soil Conservation Service of the New South Wales, that led to studies at
Hawkesbury Agricultural College. Working for the Soil Conservation Service for the next 26 years, he worked in various country towns including
Henty,
Cowra,
Goulburn,
Gunnedah and Inverell where he settled in 1987. In 1991, he was elected to
Inverell Shire Council and served three terms as a councillor and became its mayor in 1999. He became the Chairman of the Inverell Branch of the National Party of Australia in 1996 and served in that role until 1999. He became Chairman of the New England Electorate Council in 1999 and served a term during 2000 on the Central Executive of the National Party. ==Parliamentary career==