Tin (II) chloride is white while tin(II) iodide is red. Why?


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> Tin (II) chloride is white while tin(II) iodide is red. Why? 
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The answer given in my book says: 


*Bigger anion has higher polarizability; more polarization greater is the intensity of colour(valence shell electrons are loosely bound to the nucleus).* 


This answer doesn't seem to be very explanatory. Even google doesn't offer anything. It would be great if someone could explain it in a better way, focussing on the following two points:  

Firstly, how does more polarization lead to greater intensity of colour?  

Secondly, how is intensity anyways related to frequency of radiation? 


