There are a few things you have to do in order for the 1/256 chance of it's appearance and on that note there is only 1/256 chance it will also drop the ribbon (that is if you defeat it) -- now I have not defeated it as of yet. I was level 78 when I encountered it with Reddas as a guest member and with 7 characters, I didn't have a shot a killing the thing my first time through (growl)

Here's how to get it to appear (as tedious as it becomes):

First you must have control of the Strahl

Then you must take the Strahl and land on the Ozmone Plain.

You must defeat 6 or more Red and Black Chocobos in that area

Now think of Ozmone Plains as a State, you can travel through to the different cities a.k.a. areas, but if you leave the State i.e. enter Jahara or Golmore Jungle, you have to fulfill the requirements again.

You can kill the first three chocobos when you enter from the save crystal where you land from the Strahl and then head down the ramp on the left and around the bend (and Wu's) to skip to the next city a.k.a. area

From here it is easier to kill the few Mesmenir's (Unicorn like creatures) & Vipers to clear the area between for easier manuevering.

Follow the bend from the exit of Dagan Flats and go through this area (The Switchback) following the mountain on your left side and enter the next area (Haulo Green). Continue around the mountain bend and head toward the white rocks and on the left of those rocks are 3 more chocobos to kill in order to fulfill the chocobo requirement.

After that continue straight toward Jahara and in that tiny section before the Jahara entrance are 3 more chocobos. Now it is in one of these two groups of 3 that the 99 red chocobo will show up with if it shows up at all.

If it doesn't on that run through, exit back the way you came (from the Haulo Green to the Switchback and enter Dagan Flats) again, turn directly around and run through to the area the 6 chocobos live (2 areas away resets the enemies)

A few things you should know:

It will NEVER be a sleeping chocobo.
It uses Choco-comet to kill you instantly and if you remember from other games, that can't be silenced (I had to remember the hard way on try #2).
If you actually encounter it, for the love of all that is good turn off your gambits and manually kill it, gambits were my downfall on try #3 (so close, yet so far away)

My new strategy (if the silly thing will just show up again)

1) Bubble belt (in case choco-comet only deals a medium amount of damage b/c with that thing I'm at 8000 hp. (but since I think it kills you with whatever your HP is, that may not work.

2) Gambits off

3) Have member one (Vaan in my case) cast Reverse on him (to make all healing damage him)

4) Have member two (Ashe for me) cast Renew (which isn't available until after you deal with the Sun-Cryst fiasco) on him (this will bring his HP to 1 since it will have the opposite effect on him now)

5) Have member three (Penelo now) cast Cure on him (this will take his last HP point away.)

Now the only reason I think I have a shot with this is because it worked for me on a hunt once I received Renew. It was amazing and so easy since they all cast instantly one after another before the hunt could counter. That is why I hope it will work on the chocobo before he casts his choco-comet on me (and even if he does if i kill him on that run, I have the other three party members to bring in so as to not end my game).

If I finally get the red chocobo again and this strategy works, I'll post again. But I thought it would help so you had some idea of what to expect. It's become an addiction for me just to kill it. I don't even care about the ribbon, I just want to have that victory under my belt.

Happy Hunting! and I wish you better luck than I had trying all these different strategies out.