Is it permissible to conceal the eyebrows with a substance and then draw them with kohl for a specific occasion?

There is no harm in dyeing or covering the eyebrow hair with a substance and then drawing them with kohl, as the default ruling for this is permissibility, unless it involves deception towards a suitor, or if the substance prevents water from reaching the eyebrow during ablution. Sheikh Ibn Uthaymeen issued a fatwa (definition) permitting the dyeing of eyebrow hair with a color close to the skin tone, as long as there is no evidence for prohibition or dislike. It must be noted that this differs from the prohibited plucking (namṣ).