I'm glad that you said that you were intentionally playing with the colors - the drastically different looks was the first thing that jumped out at me.
I really like the first one. I think you nailed the lighting on it, I can absolutely believe that he is standing in the light of a streetlamp at dusk. I expect you've heard of the rule not to have things coming out of your subject's head (like a tree trunk, or in this case the top cap of the wall). Well, here I think breaking that "rule" works in your favor. I really like how his mop of hair stands out against the blue sky. I think that moving him to his left/camera right, so that his hair is surrounded by brick, or to his right/camera left, so that the wall cap runs through a lower part of his body, would not look as good.
While I don't like the colors of the second one nearly as much, I actually do think the vintage feel kind of works with the slight retro feel to her top. However, the muted colors and grey sky suggest an overcast afternoon to me, so the strong directional shadow behind her seems out of place.
If you don't mind, I have two suggestions regarding posing/composition. Her gaze is a touch too high IMO, she appears to actually be looking out of the top edge of the picture (and with nothing in the frame to suggest a point of interest up there, it looks forced). I'd also move her a bit more to the right in the frame. Though her head and torso are slightly right of center, suggesting that she is looking into the frame (another "rule"), there is about twice as much space between her back and the right side of the frame as there is between her foot and the left side of the frame, giving me the feeling that she's sitting too far forward.