Apart from white shirts, there are so many options to wear with light blue jackets. As long as it's not a light blue shirt.
Patterned shirts with a white ground almost always work. Just avoid too fine patterns that resolve to pale solids too close in value to the light blue of the jacket. For the contrast colour: navy, red, pink, brown, you name it.
For more casual wear, think solid linens in the colours mentioned or even wilder: orange, lime green, etc.