Blue.

Why Blue is Better (a partial list)

Almost Blue
"Am I Blue"
"Behind Blue Eyes"
"Blue Again"
"Blue Bayou"
"Blue Blue Blue"
"Blue Blue Eyes"
"Blue Cheer"
"Blue Christmas"
"Blue Clarinet Stomp"
"Blue Hour"
"Blue Monday"
"Blue Moon"
"Blue Moon of Kentucky"
The Blue Note
"Blue Ridge Cabin"
"Blue Skies"
"Blue Suede Shoes"
"Blue Velvet"
"Blue Yodel"
"Blueberry Hill"
"Bluer Than Blue"
The Blues (all of them)
"Bonnie Blue Flag"
"Deacon Blue"
"Devil with the Blue Dress On"
"My Blue Heaven"
"Rhapsody in Blue"