SET [Color] =  '#' +  CONVERT(VARCHAR(max), CRYPT_GEN_RANDOM(3), 2)

SELECT concat('#',SUBSTRING((lpad(hex(round(rand() * 10000000)),6,0)),-6))

SELECT *,
       concat('#',SUBSTRING((lpad(hex(@curRow := @curRow + 10),6,0)),-6)) AS color
FROM table
       INNER JOIN (SELECT @curRow := 5426175) color_start_point

CREATE FUNCTION `random_color`() RETURNS char(7) CHARSET latin1
BEGIN
 DECLARE str CHAR(7);
 SET str = concat('#',SUBSTRING((lpad(hex(round(rand() * 10000000)),6,0)),-6));
 RETURN str;
END;

INSERT INTO ... VALUES ( ... , ROUND(RAND(255 * 255 * 255)), ...)

with cte1 as (
select round(round(rand(),1)*15,0) as hex1,
 round(round(rand(),1)*15,0) as hex2,
 round(round(rand(),1)*15,0) as hex3,
 round(round(rand(),1)*15,0) as hex4,
 round(round(rand(),1)*15,0) as hex5,
 round(round(rand(),1)*15,0) as hex6
),
cte2 as (
select case when hex1 = 10 then 'A'
when hex1 = 11 then 'B'
when hex1 = 12 then 'C'
when hex1 = 13 then 'D'
when hex1 = 14 then 'E'
when hex1 = 15 then 'F'
else str(hex1) end as hex1h,
case when hex2 = 10 then 'A'
when hex2 = 11 then 'B'
when hex2 = 12 then 'C'
when hex2 = 13 then 'D'
when hex2 = 14 then 'E'
when hex2 = 15 then 'F'
else str(hex2) end as hex2h,
case when hex3 = 10 then 'A'
when hex3 = 11 then 'B'
when hex3 = 12 then 'C'
when hex3 = 13 then 'D'
when hex3 = 14 then 'E'
when hex3 = 15 then 'F'
else str(hex3) end as hex3h,
case when hex4 = 10 then 'A'
when hex4 = 11 then 'B'
when hex4 = 12 then 'C'
when hex4 = 13 then 'D'
when hex4 = 14 then 'E'
when hex4 = 15 then 'F'
else str(hex4) end as hex4h,
case when hex5 = 10 then 'A'
when hex5 = 11 then 'B'
when hex5 = 12 then 'C'
when hex5 = 13 then 'D'
when hex5 = 14 then 'E'
when hex5 = 15 then 'F'
else str(hex5) end as hex5h,
case when hex6 = 10 then 'A'
when hex6 = 11 then 'B'
when hex6 = 12 then 'C'
when hex6 = 13 then 'D'
when hex6 = 14 then 'E'
when hex6 = 15 then 'F'
else str(hex6) end as hex6h from cte1)

select '#'+ltrim(hex1h)+ltrim(hex2h)+ltrim(hex3h)+ltrim(hex4h)+ltrim(hex5h)+ltrim(hex6h) from cte2

SELECT '#' +  CONVERT(VARCHAR(MAX), CRYPT_GEN_RANDOM(3), 2) AS Color