You sure you didn't get the two mixed up? Terra is always associated with the color blue as far as I can remember. Zidane's only memory of his birthplace is a blue light. Everything in sight when you're on Terra glows blue. I distinctly remember Gaia being red and Terra blue. Maybe the place where you got those quotes fuddled it up?
Positive about it.

As far as comparing Garland's statements to the records in Oeilvert, I'd want to take a look at the context in which those statements are made. To be frank, I don't really remember everything else that was said, and taking single quotes out of context and comparing them while briefly referencing the rest of the argument doesn't really do it justice. It's a shame I'm too lazy to go look it up.
Full quotes.

Zidane: What is this place?
Steiner: Wh-What a disturbing room!
A face glows.
%(triangle)(square)(infinity)*+x...
Freya: Friend or foe!?
Zidane: Wait! It's saying something...
Visitors... Climb atop the stone...
(Dagger): ......
Zidane: Huh. I guess it's speaking directly into our minds.
Zidane: Well, let's go!
They stand on the platform, and it rises.
Visitors, listen well...
This is the record of our civilization...
Another face.
The seeds' decline was not our fault...
All vegetation and...vessels..died out...
The decay of our Terra... triggered it all...
In order to stop the decay, many methods were considered...
Another face.
Ultimately, the best minds of Terra's civilization gathered...
Then, a final resuscitation was attempted on the mother continent...
Unfortunately, it ended in failure...
It was later discovered to have been the catalyst... Subjects were selected...
Another face.
After four tremendous sacrifices, eternal prosperity seemed within reach...
Flora and fauna were revived, but...is still in stasis.
Final results...are still pending...


Garland: Think of it as an observatory. A place to measure the radiance of Gaia and Terra.
Zidane: What are you talking about? And what is this weird light?
Garland: That is the center of the planet. The end and the beginning of the cycle of souls.
Garland: The light remains Gaia's, for now, but when the blue changes to crimson, all will belong to Terra, and its restoration will be complete.
Garland: That is why I wrapped up the light in the Iifa Tree, to prevent the cycle of the judgment of souls on Gaia from inside the planet. Garland: Such is the Iifa Tree's true purpose, its true form. All you saw was its material form.


Zidane's group moves on. In the are with the planets colliding...

Zidane: What is this...? Two moons colliding...? No. They look more like planets. Why does this looks so familiar...?

Voice of Garland: That is a picture of Gaia being assimilated by Terra. Five thousand years ago, Terra, already an old planet, sought to assimilate Gaia. Terra needed to merge with a younger planet to survive. However, there was already life on Gaia. And so, the story begin...

Zidane: Oh yeah. I saw this in Oeilvert.

Voice of Garland: Life on Terra was coming to an end... We had no choice
but to proceed with the fusion, which tragically destroyed Terra's native civilizations. Terra was too old to assimilate everything. Thus, I created the Iifa Tree to regulate the flow of souls back to Terra.


Zidane's group moves on. In the are with the big fireball...

Zidane: Geez... That's one big fireball.

Steiner: Could it be a moon...?

Voice of Garland: This is the birth of Gaia.

Zidane; That's Gaia...?

Voice of Garland: Over 5,000 years ago...

Zidane: What's above that ladder?

Voice of Garland: See for yourself. Terra reached the peak of its prosperity at this time. The people believed that their future was secure. Ultimately, that very hubris led to Terra's demise. Thus, I was created to deal with our plights...