RTF is a global modification that replaces all towns in the game.

Gray, white, and silver – are these names or texture colors? – A white dragon is simply perceived as the opposite of a black dragon, and therefore should relate to light rather than air.
Perhaps we could use adjectives like: storm, thunder, or celestial. Or, Dragons of Ilat (the name structure is similar to Dragons of Arkat), Air Dragons, or Wind Dragons.
P.S.: "Celestial Dragon" probably won't work – it echoes "Celestial Warriors" (sky dwellers), which are units of Elrath.

http://ru.mightandmagic.wikia.com/wiki/Илат states that Ilat has white scales with a silvery sheen, so white should remain with air (a white dragon of light would look like a green dragon of darkness or a red dragon of earth). The white/black contrast can be explained as follows: the white dragon flies above the clouds, while the black dragon dwells in the deepest dungeons of the world.

Added after 4 hours 57 minutes
Or, it doesn't have to be white; I'm leaning towards storm/silver/blue or azure.
The first one simply hits hard, the second one has a chain or rainbow strike, and the third one has an electrical breath attack