When you have at texture pack on a in one snapshot and then change to another or just leave the game and then switch to the default texture pack biome specific apear gray no matter what biome you in the way I've found to fix this is to leave the game switch to another snapshot load up your world exit the game again go back to the snapshot that you where playing in before old up your world and its fixed but this is only a temporary fix so if you put the other texture pack back on and leave the game and then rejoin and switch to the default texture pack the same issue will happen again and you'll have to go though the process again to fix it.