Is defilement ruled to have transferred merely by the contact of something impure with something pure when there is wetness or moisture, even if the impurity's color or smell does not appear?

It appears you are experiencing some waswas (whispers/obsessive thoughts). It is recommended to disregard them and not pay them any attention. If you become certain that impurity has transferred to a pure place, such that its trace is visible (wetness or dampness), then you must wash away its trace. However, if you doubt the transfer of impurity, then the original state is purity, and impurity does not transfer except with certainty.