Question

If LIBr is colorless compound and CoBr2 is a blue formula of the ion that gives the blue color to CoBr2 is

Answer 1

The first statement 'LiBr is a colorless compound' , the bromide ions must be colourless.So once you get this the answr should come easy

Answer 2

Politely disagree with the previous response.

LiBr is colorless
CoBr2 has color

Notice how when the lithium was swapped with cobalt, the new compound has color. Therefore it stands to reason that it’s cobalt that gives the blue color.

To write cobalt as an ion, first find the appropriate chemical symbol for cobalt, then its charge (remembering that charges balance out in a neutral compound)