Browallia!!!

If you want something bushier, try heliotrope. Most folks are under the impression this is a full-sun plant, but I've grown it for years in part-shade and it performs beautifully.

Also, New Guinea impatiens sparkle in the part-shade. There is a soft lilac-y shade that I get every year (it's actually lilac, not pinkish).

One thing though - lighter shades of blue/lilac show well in part-shade/shade, but mid to deep blues normally don't show up that well. If you have your heart set on deeper colors (such as the standard heliotrope color or a deeper shade of browallia), either interplant with a light purple or white to make it pop.

deep blue Lobelia .... though i think it comes in other colors these days ...

link below

ken

Here is a link that might be useful: link

I second Browallia. I always use in the shade. Everytime I have ever planted it in the sun it wilts like crazy in the strong sun.

I'm trying Browallia this year - plants are coming a long nicely... But impatiens now have a "blue" hue... I tried them several years ago and although the flower was not as big as my other impatiens (I grow the larger varieties) against the a white or true pink impatien, the blue really looked blue/lilac. I wish I had a picture.

Blue torenia is my favorite annual for shade. It just never stops till frost. It can take the heat too.

Torenia is a great little plant... amazing that it can come from such tiny seed. I sowed some last year for the first time had tons of flowers later and lots of volunteer seedlings now.
Others that I am sowing this year but don't expect to bloom until next year:
Blue Jacob's Ladder
Woodland sage
Gulf coast penstemon
Great Blue Lobelia
Himalayan blue poppy (a real long shot)

Heliotrope is a wonderful blue flower for the shady border...
I'd also recommend Ageratum,with an abundance of different hues of blue flowers.....

heliotrope smells nice too. like baby powder sort of.