well,some kids sprinkled colours on our white honda city this holi,and i tried my best to remove them by washing with plain water,shampoo,VANISH(SRIDEVI ad),and even surf solution but all in vain,the spots were so dark that my car looked almost like a coloured dalmatian.then my wife told me to use her nailpolish remover on a small stain,and yes it worked(made it faint~90%).i was scared to use it as i thought it will damage the paint too,but the spots were looking so ugly,i didn't had any choice.we used 2 bottles and it took us 3 hrs for making most of them faint,then i used my deodourant too,the result was same.all of them fainted nearly 90%,and that was acceptable.
there was neither damage to the paint nor any other problem,but we can't say about long term changes as our car crashed after 1 month.so,its all up to you to use these things,cause we have experience of only 1 month we don't know much about the long term.