Strong yellow colour of `Ce^(4+)` solutions and blood red colour of `Sm^(2+)` solution arises due to :

Why is blood red in colour?

Yellow colour of faeces is due to

Yellow colour of faeces is due to :

Yellow colour of faeces is due to :

The colour of the red blood cells is due to

Why the blood is red in colour?

"When NH_(4)SCN (colourless) is added to dilute solution of FeCl_(3) (light yellow), the colour o the solution becomes deep red but on addition of NH_(4)Cl solution (colourless) the red colour faded." Why?