MySQL 8.0

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create table table_name
     (
     	json json null
     )
INSERT INTO table_name (json) VALUES ('["The Cherries:2.50","Draw:3.25","Swansea Jacks:2.87"]
     ')
SELECT json_arrayagg(json_object('name',SUBSTRING_INDEX(person, ':', 1) ,'odds',SUBSTRING_INDEX(person, ':', -1) ))
FROM table_name,
     JSON_TABLE(json, '$[*]' COLUMNS (
         person VARCHAR(40) PATH '$'
         )
         ) people;


json_arrayagg(json_object('name',SUBSTRING_INDEX(person, ':', 1) ,'odds',SUBSTRING_INDEX(person, ':', -1) ))


[{"name": "The Cherries", "odds": "2.50"}, {"name": "Draw", "odds": "3.25"}, {"name": "Swansea Jacks", "odds": "2.87"}]