Don't think the color of the moon will change. The full moon of July 31 is the second one in this month, that's what a "Blue Moon" is. The first full moon happened on July 2.
This phenomenon happens because sometimes the number of days in a calendar month are greater than the cycle of the moon, which is 29.5 days.
The chances of seeing two full moons in the same month is a rare phenomenon that takes place about every 2.6 years.