Answer:
See Explanation
Step-by-step explanation:
In the equilibrium shown in the question,on the left hand side is a pink hexaaquacobalt II complex which is pink in colour. On the right hand side, we have a tetrachlorocobalt II complex which is blue in colour.
The equilibrium can be shifted from left to right by adding HCl (a source of chloride ions).
Hence, when HCl is added to the system, the equilibrium position is shifted to the right thereby yielding the blue solution of the tetrachlorocobalt II complex.