Increasing Covalent character increases Colour intensity I observed some trends as follows:- 


$\ce{PbCl2}$ white and $\ce{PbI2}$ yellow 
$\ce{SnCl2}$ white, $\ce{SnCl4}$ red and $\ce{SnI4}$ black
$\ce{AgCl}$ white, $\ce{AgI}$, $\ce{AgBr}$ and $\ce{Ag2CO3}$ yellow


In all these cases as the size of anion increases ( polarisability increases)  or charge on cation increases (polarising power increases) colour exhibited becomes darker.. How does increasing covalent character affect this?  Or is there  any other reason?
In molecular orbital theory, as the covalent character increases the homo-lumo gap decreases, and the excitation happens more easily. Thus the colour intensity increases.