Which of the following dye is used for staining mitochondria?

Janus Green B is a basic dye and vital stain used in histology. It is also used to stain mitochondria supravitally. The indicator Janus Green B changes colour according to the amount of oxygen present. 

If oxygen is present - Indicator is oxidised to blue colour. 

If oxygen is absent - Indicator is reduced to pink colour. 

Saffranin or counter stain and crystal violets are commonly used to stain bacterial cells. 

Azure B is generally used to stain blood smear.