When it came time for us to return for World of Color, we went to the viewing area. We had to show our fastpasses several times to get there. Our seating area was "Red."
If you get to California Adventure early for your showtime, you will have to find where your color fastpass lines up before the show. For this, don't be shy and ask a cast member! Because on our way back after the show, we saw different lines all over the park waiting for the next show.
We got there a little later so we were able to just walk directly to our viewing area without waiting in line. However, since we weren't there early, there weren't many spots to pick from. While looking for a spot we found out that anyone with a fastpass could go in the Wet Zone, which is actually in the very front, so we decided to do that. It's a good spot for the show but note that it's called "Wet Zone" for a reason. Depending on where you stand and which way the wind is blowing, you could get very wet! They even have cast members in that area selling ponchos!