As long as it's done well, respraying per se shouldn't affect value - think of the number of people that have had full front end resprays because of stone chips, that never bothers anyone, and a full respray in the same colour is only an extension of this.
A full colour change to another 'standard' colour would probably be seen as questionable value for money but a full colour change to a non-standard colour would be acceptable, in my eyes at least, if it was done sympathetically and was fully documented. i.e. a full strip down, bare metal respray and rebuild