Q. Does grout turn darker when wet and lighter when dry even with color seal?

A. Unsealed grout has tiny pores that absorb moisture, which can give unsealed grout lines a darker appearance. Once the moisture evaporates (assuming the moisture is not carrying dirt and contaminants), the grout lightens back up again. A good, quality color seal fills all the tiny pores so that there is no longer any space for moisture. So the answer is no, color sealed grout will not get darker when wet or lighter when dry. The appearance of color sealed grout remains consistent. The only exception would be if there is a moisture problem underneath the grout. In that case, you would want to have the moisture problem resolved first, then have the grout color sealed after.