Blue and white to get the desired shade. The more white you add the lighter shade of blue you will get. If you want a bit of violet, add a dash / drop of red.
Since blue is a primary color there are no two colors to mix to create blue so you would just have to use a darker color blue and white.
The colors you mix with sky blue to get navy blue would be a dark blue or a black. These will make a navy blue.
Yellow and Blue.
Red and blue make purple.
red and blue
yellow and blue.
blue
none
Red, blue and green make yellow
You cannot mix any color with blue to get red. Blue and red are primary colors.
To make light blue mix blue with white. Start with the white and add a little blue at a time until you have the shade you want.
blue & red. blue & red.