The spiked wind serpents only had a couple colors available prior to Mists of Pandaria even though there were other unused colors in the game files for years. Blizzard remedied this by scattering a bunch of new rares in 5.1 and 5.2 to get some of those colors in the wild.
Sparkwing, pictured above, is the only wind serpent to use the blue/white skin. It spawns at about 59,86 inside a cave in Stonetalon Mountains. As with most old world rares added in Mists, its respawn time seems to average around 3-4 hours. Wind Serpents have Lightning Breath (magic vulnerability) as their special ability, and it’s going to stay the same in Warlords.
You may also remember this blue guy from the T15 2-piece bonus that summoned a Thunderhawk (which always seemed to shoot the wrong target, am I right?).