Reverse Substring the value with the position

I have data

col1
[{value -> Apple, key -> Fruit}, {value -> White, key -> Colour}]
[{value -> Mango, key -> Fruit}, {value -> Black, key -> Colour}]

and I wanted to extract a value

value -> White
value -> Black

select col1, instr('key -> Colour' in col1), substr(col1, instr('key -> Colour')
from 
(SELECT '[{value -> Apple, key -> Fruit}, {value -> White, key -> Colour}]' as col1 from dual
union all
SELECT '[{value -> Mango, key -> Fruit}, {value -> Black, key -> Colour}]' as col1 from dual
) tbl;

I have tried using position and substring, unable to get, any suggestion would be appreciated.

Basically need to search for a value key -> Colour and extract the value by reverse substring till { which will get me the value value -> White and value -> Black

You can start the search with value -> <value> ending with key -> Colour using REGEXP_SUBSTR, and then replace the ,key -> Colour using REGEXP_REPLACE

select col1, 
REGEXP_REPLACE
(REGEXP_SUBSTR
(col1, 'value -> [^,]*, key -> Colour'), ', key -> Colour') AS new_val

from 
(SELECT '[{value -> Apple, key -> Fruit}, {value -> White, key -> Colour}]' as col1 from dual
union all
SELECT '[{value -> Mango, key -> Fruit}, {value -> Black, key -> Colour}]' as col1 from dual
) tbl;

Fiddle