write a fraction using the coloured boxes.

A fraction generally has a numerator and a denominator. 

The numerator tells the part of the value and the denominator tells the whole value. Considering the square with coloured and uncoloured boxes. 

As a whole, the square has 16 boxes. Among the 16 squares, 8 boxes are coloured and the remaining are left uncoloured. 

So the fraction can be written as $\frac{8}{16}$

Thus, the correct option is A