Its white because, for some reason, its not producing chlorophyll. Two thoughts: its still living off the stored energy in the seed but will start turning green when it needs to. Giving it some bright light may move it in that direction.
A wee bit of fertilizer may help also (anything you have but a quarter to half strength)
Or.. Its a mutant and incapable of producing chlorophyll. If it doesn't soon though, when the seed shrivels, the plant will die.
