(Updates with final prices, details of Mexico rate hike) By Bru** Federowski SAO PAULO, Sept 29 (Reuters) - The Colombian peso rose onThursday on optimism that OPEC's plan to cut oil output for thefirst time in eight years could support crude prices, but theMexican peso fell in spite of an expected interest rate hike bythe central bank. The Organization of the Petroleum Exporting Countries agreedon Wednesday to cut output to 32.5 million-33.0 million barrelsper day (bpd) fr