I made my shorts white.
For the shirt, when I cosplayed as Sasuke, I used a sweatshirt pull-over pattern, making the collar (the basic shape was provided in the pattern) slightly taller and wider, and I shortened the sleeves to t-shirt length. The collar was made stiff using interfacing, which was sewn between the outer blue and the inner white lining.
There's my Sasuke costume. Its not the greatest photo, but (unfortunately) its one of the only ones I have, since I didn't take too many pictures of myself in that costume.