If the lanthanoid element with xf electrons has pink colour, then the lanthanoid with (14 − x)f electrons will have the colour

pink

The correct answer is option 4. pink.

The color of the ions depends upon the number of unpaired electrons. If xf and (14-x)f both have the same number of unpaired electrons, then they will both have the same color.

In the case of the lanthanide elements, the f-orbital can have a maximum of 14 electrons. If the lanthanide element with xf electrons has pink color, then it has 2 unpaired electrons in the f-orbitals. This means that the lanthanide with (14 - x)f electrons will also have 2 unpaired electrons in the f-orbitals.

Therefore, the lanthanide element with (14 - x)f electrons will also have pink color.