I should just mention, since sometimes people come across this in tantra and it can be quite confusing, that in the highest class of tantra, we speak about white and red bodhichittas. Now, these are forms of very subtle material phenomena, physical phenomena. These are not states of mind.
These are very subtle… difficult to find a good word, but let us call them sparks of creative energy that each of us has. And in the highest class of tantra, in the very advanced stages of it, once we gain the ability to do this—which is incredibly difficult to gain, that ability—then we can move these very subtle creative energies within our body and dissolve them into the heart chakra in order to be able to achieve or access the subtlest level of mind. It’s called the clear light mind (’od-gsal). And then use that for focusing on voidness and achieving enlightenment, because it’s the most efficient level of mind.
And so these are substances and methods that we work with, these white and red bodhichittas, in order to actually achieve deepest bodhichitta, this clear light mind focused on voidness. And so often in Buddhism the name of the result is given to the cause, they say, and so the result—which is bodhichitta, deepest bodhichitta—that name is given to, as an alternative name, to these two types of creative subtle energy within the body. That’s what is white and red bodhichitta—are why they’re called bodhichittas.
Just so you don’t get confused, because I know that can be terribly confusing when we come across those names. At our level of practice, this is something we are not at all involved with. Very, very advanced. Also, so that people don’t get confused, both men and women have both white and red bodhichittas. And so although there are different levels of grossness of it, we shouldn’t associate them with the grossest representations of them and think that only men have one and only the wife [or] only women have red; that’s incorrect.
Source: http://www.berzinarchives .com/web/en/archives/sutra/level2_lamrim/advanced_scope/bodhichitta/overview_6_far_reaching_attitudes/part_1.html