My only nightmare is waking up alone
In a world where you’re not mine
And the room painted off white
Running out in the daylight, tryna get back to you
Frank reveals that his only fear is that something he dreamed about will come true, the day his girl leaves him.
The walls painted all white is a reference back to the line about painting the walls back, Frank is saying that if the walls are painted white, the the light their love made has died.
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