Does the landlord of an apartment have to paint every time a new tenant moves in? Furthermore, is there any difference in laws or rules regarding painting between large apartment buildings (nine or more units) to privately owned homes (3 or less units)?
A LL doesn't have to paint every time a new tenant moves in.
The general housing maintenance code provides that the internal parts of an apt are to be painted every three years (or less if in the lease).
In the case that an apt is a funky color because a prev. tenant painted and the new tenant can't stomach it, the LL should have it repainted and take the cost from the prev. tenant security deposit. It would have to be a non-neutral color to justify that though -- red, green, black, bright yellow etc. I think.