Find the odd one out : iodopsin ,rodopsin ,haemoglobin ,glucagon

Dear srudent
​​​​​​Please find your answer below to the asked query:

Haemoglobin - red pigment for o2 transport,
Iodopsin - the cone pigment system in chicken retina
Rhodopsin is a biological pigment found in the rods of the retina 

Glucagon is a peptide hormone

Glucagon is odd one out as it is hormone and all others are pigment.

Regards