Why are babies dressed in white during a Roman Catholic christening (aka baptism)? Is the color symbolic or anything? Can any other color be worn? Similarly, are there some sort of color restrictions for adult converts?
The color white is primarily symbolic of the pure state of the baby's/adult's soul along with the renewal of life after being cleansed of original sin by the Holy Spirit. But as with all symbolism, there are many more things associated with the color (according to Wikipedia):
According to surveys in Europe and the United States, white is the color most often associated with innocence, perfection, the good, honesty, cleanliness, the beginning, the new, neutrality, lightness, and exactitude.
There are no official Catholic teaching on the color of clothing, but people may choose white on account of the tradition and symbolism of the color.