1) Is it allowed for us to use temporary hair color, which is removed with water over time? Its not an obstacle for gusl?

2) If we have kajol in our lower lashes,  makes wazou batil? Is the lashes has to be obligatory wet ?

1- If it is only a die, which only colors the hair, and do not prevent water reaching the hair, then it is allowed.

2- Water has to reach the lashes. If kajol is an obstacle, then, it has to be removed before wodou or gusl.