In low spirits
Dark and depressing
Tending to cause sadness or low spirits
Bordering on indelicacy or impropriety
One of the primary colors
She handed him a light blue shirt.
Those blue eyes were boring into her soul, searching for heaven only knew what.
The bright blue eyes regarded her thoughtfully.
It had a bright blue cover, which he was careful not to soil.
This zinger out of the blue took me aback.