Does impurity vanish and the remaining yellow color become pure after pouring water and scrubbing the place of urine twice with soap?

Pouring water over the entire ritually impure area of the carpet is sufficient to purify it. If you doubt whether the yellow color is a trace of impurity, the default assumption is purity. However, if you are certain that it is a trace of impurity, then you must purify that area until its color disappears. If you suffer from obsessive doubts (waswas), do not give in to them.