Combine vinegar, sugar and mint, tied in cheesecloth, in saucepan. Heat gently 10 minutes; remove from heat.
Stir in food color. Add onions and pimientos; heat to boiling. Remove mint. Pour into hot jars; adjust lids. Process in boiling water bath (212°) 5 minutes. Remove jars and complete seals unless closures are self-sealing type.