Colours

One characteristic of transition metals is that their compounds are coloured.

The colour of the solids in the images below is in each case due to the presence of the transition metal ion given in brackets after the compound name.

iron(II) sulfate (Fe²⁺)
very pale green solution

potassium

(MnO₄^–)
purple solution

iron(III) nitrate (Fe³⁺)
very pale purple solution

manganese(II) sulfate (Mn²⁺)
very pale pink solution

Two of these solids contain ions that are reactants in a titration of Fe²⁺ with MnO₄^–.
The other two solids contain ions that are the transition metal-containing products of the reaction.

In each case the intensity of the colour in the solid is much greater than its aqueous solution at concentrations of 0.2

or below used in a titration.
However, despite this, the images show that

there is a dramatic change in colour from reactants to products.
the colour of the solution in the titration flask will depend on how much titrant has been added

Thus no additional indicator is needed in iron(II) -

titrations to detect the equivalence point. It is important to note that this is not necessarily the same as the end point.

At the equivalence point chemically equivalent amounts of reactants and products are present.

The end point is the point in the titration at which a colour change occurs.

Ideally the end point and the equivalence point occur at the same or very close to the same added volume of titrant.,