Yes it is safe. Topical tarcolimus has been used in cases where oral lichen planus has been resistant to treatment by topical corticosteroids. However, very few cases have been reported in literature of mucosal pigmentation associated with the use of topical tarcolimus.
The first option is the dermocorticoid considering the increased knowledge of long-term side effects.
However the 0.1% tacrolimus oinment or 1% orabase are also effective but it should be considered that the drug is relatively new and there neoplasia reports (Radfar et al. 2008) with extended use.
I also remember the pimecrolimus, cyclosporine and aloe vera as an alternative to topical treatment