Coleus forsokolii - Plectranthus barbatus - Indian Coleus
This furry giant from Madagascar puts out long stems of the bluest flowers imaginable, lots of them. It towers over your head, spreads to cover a wall, and is one of the most spectacular bloomers I've ever seen.
Though not a Salvia, it has the same appeal and works well in a salvia garden. Also known as Coleus forskohlii, the lime green leaves are thick and fuzzy, and it delivers 10" spikes of electric purple-blue blossoms from fall through spring. Perennial in zones 8-10, it's easy to grow. A frost will level it, but it reaches full blooming size quickly and you can enjoy it as an annual anywhere.
Indian Coleus is perfect for gardens with dramatic plants like Brugmansias, and is a great backdrop for your salvia spread. Plant it against a wall for support and shelter, or show it off in a container. Full or partial sun, rich soil, average water. This is one amazing plant.