Grön eld verkar bara vara att resa med Floo Network.

För att resa via Floo Network används Floo Powder, vilket gör att elden grön och sänker temperaturen för att göra det möjligt att komma in i elden.

“Incendio!’ said Mr Weasley, pointing his wand at the hole in the wall behind him. Flames rose at once in the fireplace, crackling merrily as though they had been burning for hours. Mr Weasley took a small drawstring bag from his pocket, untied it, took a pinch of the powder inside and threw it onto the flames, which turned emerald green and roared higher than ever. ‘Off you go then, Fred,’ said Mr Weasley.”
- Harry Potter and the Goblet of Fire, Chapter 4 (Back to the Burrow)

När människornas huvuden dyker upp i eldstaden, nämns emellertid inte flammeskiftfärgen.

“Amos Diggory’s head was sitting in the middle of the flames like a large bearded egg. It was talking very fast, completely unperturbed by the sparks flying around it and the flames licking its ears.”
- Harry Potter and the Goblet of Fire, Chapter 11 (Aboard the Hogwarts Express)

Sirius hade letat efter när han kunde prata med Harry, vilket skulle ha varit mer uppenbart för alla om elden blev grön när han dök upp.

“Because I’ve just seen Sirius’s head in the fire,’ said Harry. He spoke quite calmly; after all, he had seen Sirius’s head in this very fire the previous year and talked to it, too; nevertheless, he could not be sure that he had really seen it this time … it had vanished so quickly …

‘Sirius’s head?’ Hermione repeated. ‘You mean like when he wanted to talk to you during the Triwizard Tournament? But he wouldn’t do that now, it would be too – Sirius!’ She gasped, gazing at the fire; Ron dropped his quill. There in the middle of the dancing flames sat Sirius’s head, long dark hair falling around his grinning face.”
- Harry Potter and the Order of the Phoenix, Chapter 14 (Percy and Padfoot)

Dessutom är den gröna elden inte så varm, elden runt huvudet är fortfarande.

“Sirius!’ he said. Harry whipped round. Sirius’s untidy dark head was sitting in the fire again.

‘Hi,’ he said, grinning.

‘Hi,’ chorused Harry, Ron and Hermione, all three kneeling down on the hearthrug. Crookshanks purred loudly and approached the fire, trying, despite the heat, to put his face close to Sirius’s.

‘How’re things?’ said Sirius.”
- Harry Potter and the Order of the Phoenix, Chapter 17 (Educational Decree Number Twenty-four)

Elden verkar också vara grön när personen som reser med Floo anländer till målplatsen.

“The Atrium was full of people; the floor was reflecting the emerald green flames that had burst into life in all the fireplaces along one wall; and streams of witches and wizards were emerging from them.”
- Harry Potter and the Order of the Phoenix, Chapter 36 (The Only One He Ever Feared)

När Dumbledore anländer med Floo, är den brand han ser i också grön.

“The empty fireplace burst into emerald green flame, making Harry leap away from the door, staring at the man spinning inside the grate. As Dumbledore’s tall form unfolded itself from the fire, the wizards and witches on the surrounding walls jerked awake, many of them giving cries of welcome. ‘Thank you,’ said Dumbledore softly.”
- Harry Potter and the Order of the Phoenix, Chapter 37 (The Lost Prophecy)

Elden är grön (och inte het) för den som gör samtalet.

Vi får se detaljerna om hur ett eldstedsanrop fungerar när Harry försöker ringa Sirius från Umbridges kontor. Den person som gör kaminen använder Floo Powder och klibbar huvudet i smaragdgrön eld, men elden på mottagaränden förblir varm och orange.

“Harry pulled off his Cloak and, striding over to the fireplace, found what he was looking for within seconds: a small box containing glittering Floo powder. He crouched down in front of the empty grate, his hands shaking. He had never done this before, though he thought he knew how it must work. Sticking his head into the fireplace, he took a large pinch of powder and dropped it on to the logs stacked neatly beneath him. They exploded at once into emerald green flames.

‘Number twelve, Grimmauld Place!’ Harry said loudly and clearly. It was one of the most curious sensations he had ever experienced. He had travelled by Floo powder before, of course, but then it had been his entire body that had spun around and around in the flames through the network of wizarding fireplaces that stretched over the country. This time, his knees remained firm upon the cold floor of Umbridge's office, and only his head hurtled through the emerald fire …

And then, as abruptly as it had begun, the spinning stopped. Feeling rather sick and as though he were wearing an exceptionally hot muffler around his head, Harry opened his eyes to find that he was looking up out of the kitchen fireplace at the long, wooden table, where a man sat poring over a piece of parchment.”
- Harry Potter and the Order of the Phoenix, Chapter 29 (Careers Advice)

Det här är lite meningsfullt - att kunna hålla huvudet i brand, den som ringer skulle behöva använda Floo Powder så att huvudet skulle transporteras och inte brännas.