Are you sure the original tiles aren't white?..my neighbor has a white
roof and everytime he has it pressured washed i'm amazed that it was
actually white. No idea how they paint them, it would seem like
concrete acid wash, then concrete stain would be longer lasting, but if
your new tiles have some type of ceramic coating seems you would need
something more paint like it would seem.

I think you're going to have to do some calling around on this. I just
went out and looked at that nieghbors roof who had thiers painted or
coated or whatever, its been 2 years and still looks very good...so i
dunno maybe they can get 8 years or so out of whatever it is they do?
Theres alot of houses arond here who do it, i'm just nervous of
creating another major chore..