Coba ini:
SELECT * FROM wp_posts AS p
LEFT JOIN wp_term_relationships AS tr ON p.ID = tr.object_id
LEFT JOIN wp_terms AS t ON tr.term_taxonomy_id = t.term_id
WHERE p.id IN
(
SELECT p2.id FROM wp_posts AS p2
LEFT JOIN wp_term_relationships AS tr2 ON p2.ID = tr2.object_id
LEFT JOIN wp_terms AS t2 ON tr2.term_taxonomy_id = t2.term_id
GROUP BY p2.id
HAVING FIND_IN_SET('blue', GROUP_CONCAT(t2.term)) AND FIND_IN_SET('old', GROUP_CONCAT(t2.term))
)
