How to use GROUP_CONCAT in a CONCAT in MySQL

If I have a table with the following data in MySQL:

id       Name       Value
1          A          4
1          A          5
1          B          8
2          C          9

how do I get it into the following format?

id         Column
1          A:4,5,B:8
2          C:9

I think I have to use GROUP_CONCAT. But I'm not sure how it works.

 Answers

select id, group_concat(`Name` separator ',') as `ColumnName`
from
(
  select id, concat(`Name`, ':',
  group_concat(`Value` separator ',')) as `Name`
  from mytbl
  group by id, `Name`
) tbl
group by id;

Update Splitting in two steps. First we get a table having all values(comma separated) against a unique[Name,id]. Then from obtained table we get all names and values as a single value against each unique id 

Edit There was a mistake in reading question, I had grouped only by id. But two group_contacts are needed if (Values are to be concatenated grouped by Name and id and then over all by id). Previous answer was

select 
id,group_concat(concat(`name`,':',`value`) separator ',')
as Result from mytbl group by id

---

SELECT ID, GROUP_CONCAT(CONCAT_WS(':', NAME, VALUE) SEPARATOR ',') AS Result 
FROM test GROUP BY ID

---

 SELECT id, GROUP_CONCAT(CONCAT_WS(':', Name, CAST(Value AS CHAR(7))) SEPARATOR ',') AS result 
    FROM test GROUP BY id

you must use cast or convert, otherwise will be return BLOB

result is

id         Column
1          A:4,A:5,B:8
2          C:9