Is it possible to match mortar colour to make it similar colour to old/existing brickwork mortar without compromising on strength of mortar? What are the important ingredients of the mortar mix that determines the colour?

Colouring only determines the colour.
The colour ingredients have no effect on the strength of the mortar.
It is very possible to mix the right colouring.

I think this is a test question. Can you word the question better.