SELECT id HAVING maximum count of id
SELECT color_id
FROM
(
SELECT color_id, COUNT(color_id) totalCount
FROM products
WHERE item_id = 1234
GROUP BY color_id
) s
HAVING totalCount = MAX(totalCount)
UPDATE 1
SELECT color_id, COUNT(color_id) totalCount
FROM products
WHERE item_id = 1234
GROUP BY color_id
HAVING COUNT(color_id) =
(
SELECT COUNT(color_id) totalCount
FROM products
WHERE item_id = 1234
GROUP BY color_id
ORDER BY totalCount DESC
LIMIT 1
)
- SQLFiddle Demo (having tie)
SELECT color_id AS id, COUNT(color_id) AS count
FROM products
WHERE item_id = 1234 AND color_id IS NOT NULL
GROUP BY color_id
ORDER BY count DESC
LIMIT 1;
This will give you the color_id and the count on that color_id ordered by the count from greatest to least. I think this is what you want.
for your edit...
SELECT color_id, COUNT(*) FROM products WHERE color_id = 3;