# Question #0ae0f

When you add the indicator it binds to the metal cations present. As you add $\text{EDTA}$ by titration, the $\text{EDTA}$ binds to the metal complex present, displacing the BOUND $\text{Eriochrome Black T}$.
When the indicator was bound as a complex, the colour was red; the free base is blue. $\text{Eriochrome Black T}$ is simply another indicator, whose acid and base forms are differently coloured.