I think it should be 'black heart' both times around, but I like to think of the second time as 'black out'. To me this song, especially the first verse, relates somehow to depression.
"We see the shadows that are falling from your eyes" -- yes, you are tired as hell
"Draining your face of everything but the disguise" -- but you try to keep a straight face and go through it alone
"Don't hide baby, let them see your true colours
Don't mind the camera, let them see your black heart tonight" -- the camera represents that there's always people watching, and everything you do out of normal will be remembered, but ignore that and release your pain
"Don't hide baby, show them just how deep it goes" -- sure does.
"Don't mind the cameras, let them see your black out baby" -- when it becomes too much
I think it should be 'black heart' both times around, but I like to think of the second time as 'black out'. To me this song, especially the first verse, relates somehow to depression. "We see the shadows that are falling from your eyes" -- yes, you are tired as hell "Draining your face of everything but the disguise" -- but you try to keep a straight face and go through it alone "Don't hide baby, let them see your true colours Don't mind the camera, let them see your black heart tonight" -- the camera represents that there's always people watching, and everything you do out of normal will be remembered, but ignore that and release your pain "Don't hide baby, show them just how deep it goes" -- sure does. "Don't mind the cameras, let them see your black out baby" -- when it becomes too much
my interpretation only, though.