Eyelash perming/tinting is halachically comparable to perming/dyeing one's hair, which is permissible and is not considered a chatzitzah as long as the dye is complete.

If the dye is no longer complete nor aesthetically pleasing, ideally one should retint prior to mikveh (preferably a few days before, to allow any excess dye to wash off). If one did immerse without retinting, the tevilah is valid as long as there is no physical barrier from the tint (i.e., the dye is fully absorbed into the lashes and you cannot feel it with your fingers).

Please feel free to get back to us with any further questions.