$(B)$ $\left[{Fe}({SCN})_{6}\right]^{4-} \rightarrow$ Blood red colour
$(C)$ ${Fe}_{4}\left[{Fe}\left({CN}_{6}\right)\right]_{3} \cdot {H}_{2} {O} \rightarrow$ Prussian blue
$(D)$ $\left[{Fe}({CN})_{5} {NOS}\right]^{4} \rightarrow$ Violet colour