I beg to differ....
My preference has always been towards white cars after having
owned quite a few, as well as many other coloured vehicles.
Black shows the dirt the quickest...
Dark colours also show up the dirt too...
Paler colours get away with the 'first' sign of dirt as there are
many shades of the lighter colours around.
But white gets away with it best, as there are many many tones
of white through to the creamy sort of colour it will get to when
it is really dirty.
TBH, with white you can only see the 'first levels' of dirt when you
get 'up close n personal' to the vehicle.
So having said that....wash it whenever you like
mr singh