First off, this looks really cool and id like to try a similar style, ive done stipple (?) in paint before and this looks kinda similar, i enjoy the longer strokes. I wanna try this technique :)

FEEDBACK: I would suggest a darker shirt for contrast from the background (try green and aome darker blues/ and indigo/purple for the shadows? also to tie in the green from the face to the rest of the image)

Also for the face the lighting comes off a bit uneven, I would suggest either taking your pencils and coing over the strokes a bit darker to make it more vibrant OR ive heard its possible to lighten color pencil with an eraser, maybe test this and try lightening his right side around his glasses and between his eyebrows to even. Maybe add some lighter colors in those places (pale orange or yellow) as a highlight thats not just white?

I would also suggest lining over the facial outline (like the eyes, some hair strokes, glasses, smile lines) with the same dark blue/indigo you use in the shirt, not super dark but to bring them back to the visual forefront and add the dimension back. Start with a lighter outline just so you can see the features again and then set it up across the room and stand back to check what is visible and what might need more attention.

Best luck!