Someone who would easily notice the intonation issues and further comment on it, must be the creator. :) After listening to everyone's submissions countless times, I'm still happy with this as my vote.
I didn't imagine black and white, personally, but more of a monochromatic red. When the harp harmonics combine with the bass, there is a definite lightening of the red. As for why the color red? Emotion. This one was filled with it - and aah it's so beautiful. Other than that, I can't explain why red came to mind instead of any other color. (I suppose now that it's revealed it had to do with love, well...)
I also didn't imagine the harp representing the woman and the bass representing the man-- What I saw was, in the beginning, a light, fading red, and the bass by itself, a deep, dark red. When they combine in the third segment, the shades continue to decrease and increase, back and forth, in lightness. This is my definition of monochromatic, in its strictest sense. However, it's nice to have a story to go along with it, like you provided above :)
In my opinion, this piece is one of the best examples of a visual concept being applied to an aural one. I posted a similar comment on SkyeWintrest's mock submission, as yours and his do really well with the theme, at least in my eyes. Or rather, ears.
Very beautiful playing of that double bass, by the way. How long have you been playing?
Can't wait to hear your second and third pieces! ^^