There are only like 6 common extract types - Amber, Pale, Light, Dark, Munich, and Wheat.
Amber, Light, and Pale are all pretty close to the same color. Munich and Wheat are only a few shades off. Dark is the only one that is a stark contrast to the rest.
So, unless you are brewing extract stouts or porters, you would expect pretty much all extract to be fairly close to one another EXCEPT for whatever specialty grains the recipe includes.
If you are brewing similar styles, the law of averages would dictate that they would come in all pretty close to the same color using extract recipes.
That's all I can think of. The majority of the color comes from the extract and specialty grains. The water shouldn't affect color at all (unless you are using Mexican water!).