Captain America would be an ideal candidate to wield the blue light of hope and become a member of the Blue Lantern Corps.
As Americas World War II super-soldier, Captain America was a symbol of freedom and hope in the fight against the Nazis. I cant think of a better example from the whole of fiction to wield a Blue Lantern ring, let alone from Marvel.
With his fantastic leadership skills, tactical proficiency and ability in the field of battle, Captain America would make a fine Blue Lantern and it would be great to see him wielding some real power to compliment his bravery and skills as a fighter, rather than merely operating at the peak of human potential.
The fact that his costume is predominantly blue already just makes it all the more fitting.