Ln(III) compounds are generally colourless
Because of the large size of the Ln(III) ions the bonding in its compounds is predominantly ionic in character.
The ionic sizes of Ln(III) decrease in general with increasing atomic number.
Ln(III) hydroxides are mainly basic in character.
Most of the Ln(III) compounds are coloured due to f-f transition in solid as well as in aqueous phase. So, Ln (III) compounds are generally colourless is a wrong statement.