SELECT R,G,B
FROM(
SELECT R,G,B,(testing.USAGE) as u
FROM testing order by sqrt((pow((R - 100),2)+pow((G - 100),2)+pow((B - 100),2))) LIMIT 5) as AAA
WHERE u = (SELECT MIN(u) FROM AAA);

SELECT * FROM photomosaic.testing
where testing.USAGE = (SELECT MIN(testing.USAGE) from testing);

select * FROM(
SELECT  R,G,B,(testing.USAGE) as u,sqrt((pow((R - 200),2)+pow((G - 200),2)+pow((B - 200),2))) as AAA 
	FROM testing  order by AAA LIMIT 5) as a order by u limit 1;