In simple terms, if the film is under-exposed (e.g. rated higher), and equivalent amount of over-development is suggested. Or, if the film is over-exposed (e.g. rated lower), the corresponding under-development is suggested. Both color fidelity and contrast will be affected. Whether the result is still acceptable is a matter of personal taste. Note that the color temperature of the taking light can't really be compensated for in processing, but only via filtration.