Hello sharonanyc, and welcome to TripAdvisor and the Pasadena forum.
Congratulations on securing those fabled grandstand tickets! This is where the television cameras will be at and networks will be broadcasting from. . . they've done so from this location for decades.
Yes, you need to be in place with your car parked on Green Street south and parallel to Colorado Blvd. by 6:00 AM, and your body needs to be in the stands by 6:30 AM. It gets crowded along the parade route, and the key thing is to get in place in time so as to not delay the Tournament of Roses Parade. Hence getting there up to two hours before the stated start of the parade, which is 8:00 AM at your location at Colorado and Orange Grove.
The way I would do it myself given your situation, and I've been to several previous Rose Parades in the past, is to get there maybe an hour earlier, since you've got parking arranged and a bleacher seat ticket given out to you. Bring your coat, gloves, and hot cider or other hot beverage of choice (no alcohol). . . and maybe some reading material. The time goes faster that way. Some breakfast munchies on the go like a muffin, too.
To broaden the discussion beyond the particular street location of the Original Poster, I offer these tips:
For those folks without a parking space arranged, and without a bleacher seat, I would recommend getting there in the 3:00 AM to 4::00 AM time frame. Think about where you will park, north or south of Colorado Blvd. and which side of the street you want to view the parade on. Crossing Colorado Blvd. is not a good working strategy imho. Park and watch the parade from the same side of the street. Colorado Blvd. gets shut down to pedestrians crossing around an hour before the parade comes through give or take. Yes, you will have to walk a number of blocks to get to the parade and then back to your car. Exercise to start the New Year out right, eh? (wink)
Enjoy your visit to the Queen City of Pasadena.