If the jacket is dark brown make sure the pants aren't also really dark blue or the combination will look muddled. If the jacket is lighter, more towards tan/khaki, then light blue can work since the colors stay separated even in lighter hues, but dark blue pants will work too.
A man is standing against a white background, wearing a navy blue blazer, a striped tie, and khaki pants. He has a serious expression and is looking directly at the camera.
A man is standing against a white background, wearing a navy blue blazer, a striped tie, and khaki pants. He has a serious expression and is looking directly at the camera.