Is the bottom of a sandal purified by immersing it in the waters of muddy ponds that have changed color due to street dust?

For a shoe that has been affected by water to be deemed impure, the substance of the impurity must be removed. Merely running water over the shoe is sufficient to remove the impurity. The discoloration of the water by dirt does not matter, unless it becomes thick mud, at which point it can no longer be called water. If it reaches this stage, it is no longer a purifier.