Lion Turtles have different markings on their forehead to distinguish between different elements:
Lion turtles associated with fire have two swirls curling inward, forming a shape similar to a heart
Lion turtles associated with air have a more intricate swirling pattern, with two swirls curling outward and a swirl in the center
Lion turtles associated with water have three wavy lines increasing in length from top to bottom and a lone swirl underneath
Lion turtles associated with earth have a singular swirl diverging into two smaller swirls, with the one on top larger than the other, forming a shape similar to a question mark. In addition, the lion turtles associated with earth have two swirls on each upper cheek and two others near their ears.
So all we have to do is take a look at the forehead of the Lion Turtle Aang was talking to:
And we can see the two swirls curling inward, forming a shape similar to a heart, meaning that this Lion Turtle is one that, back in the day, granted humans the power of fire. This makes sense, as the crew were on Ember Island in the Fire Nation when the Lion Turtle first appeared.
I personally like to believe that this is the same Lion Turtle that first gave Wan the power of fire all those years ago.