codice:
SELECT catalogo.id, catalogo.nome, catalogo.color1, colori.descr, colori2.descr, colori3.descr
FROM ((catalogo INNER JOIN colori ON catalogo.color1 = colori.codice) INNER JOIN colori AS colori2 ON catolog.color2 = colori2.codice) INNER JOIN colori AS colori3 ON catolog.color3 = colori3.codice