dear ahsan bhai
first of all ye zeyaditi hai to mention my name in expert lists, i am same like u a learner
experts already gave their feedbacks and pictuers which are self explanatory and without doubt they darken silver colour to medium silver.
well experts did very hard working and time to change colour, i can tell u very secret , easy and fast recipe 
use 3m polishing pad glaze for dark colours and topup with dodo juice purple haze wax :P;)
hey dont be serious i am just kidding 
as amir bhai , usman bhai already guided by using more and more natural waxes, glazes u can darken the lighter shades, as amir bhai said its not easy task so patience and natural waxes /glazes are keywords
colour choice is something personal liking disliking and to change them in our own control, some like darken depth and some like sharp , crisp reflections
i personally like lighter shades more clearity , vivid, sharp, crisp shine and reflections with further lighten colour tone good examples are
for silver once usman bhai did silver merc and kashif bhai's frosty white city
ofcourse lighter shades also need natural oils for enriching paints ( wet touch ) so purified natural waxes would be best choice some examples would be dodo juice supernatural ( for silver ) dodo juice white diamond ( for white ) dodo juice light fantastic ( for all light colours , pinnacle souvern liquied wax best natural wax for light tones without changing colour tone.
on other hand for dark/ sharp tones like black, red, blue etc my choice is depth / colour darkening, deep rich gloss instead of reflections ( or iss ka sara guna amir bhai ko jaye ga )
so its all depend upon u , what u wish to divert ur paint tone 
