A water rinse with color will slow down development based on diffusion with the top layer slowing first, the next layer and etc until the bottom layer is reached. Therefore there will be a color shift. It will be on the blue-red axis usually or yellow-cyan depending on the film and process.

Water is not the determining factor in using a rinse after development. Water diffuses inwards at a given rate, and the developer chemistry begins moving outward slowly. Carbonate and Borate are huge molecules and diffuse slowly and HQ and Metol are also large. So, incoming water is rapidly lowered in pH by the slow moving alkalis, and the slow moving developing agents may then continue to react as pH continues to be high and then slowly drops.

OTOH, a hydrogen ion, present in abundance in an acidic solution will reach the bottom of the film or paper faster than any other ion. This movement is virtually instantaneous. It can take 15" to 30" for the other chemicals to diffuse that distance.

An easy way to check this out is to dip a piece of fogged unprocessed film into developer. Watch the BACK of the film and look for the back to begin development. Compare that time to the same change on the FRONT of the film under the same conditions. That is how long it takes for development to start (and stop). This is rough, but will show you the effect in most cases.