I've used LightMountain Henna too. My hair is dark brown/auburn with some red highlights. I've started getting a fair amount of white recently....

The henna definitely doesn't cover the white, just makes it faintly red. My hair is dark enough that it still shows pretty plainly. I'm resisting any type of color that is permanent as once you start you are stuck and I wouldn't be able to stand the upkeep. Plus the choices are definitely limited if you don't want to expose yourself to a lot of chemicals.

Maybe some time I'll be vain enough to try the LightMountain that covers greys. I don't feel old enough to have a head of white hair... and I don't want to give up having longer hair either, though I'm afraid that the texture is also changing. The whites are less curly and more just wild....