Praise be to Allah.
There is nothing wrong with that, because the basic principle is that things are permissible, so long as it is not done to deceive a suitor, in which case it is not permissible.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked about the ruling on dyeing the eyebrows with a colour similar to that of the skin. He replied: There is nothing wrong with that, because the basic principle regarding such matters is that they are permissible, so long as there is no evidence from the Qur’an or Sunnah to indicate that it is haraam or disliked (makrooh).
End quote from Fataawa ash-Shaykh Ibn ‘Uthaymeen, Majallat ad-Da‘wah, no. 1741, 7/2/1421 AH, p. 36.
There is no difference between dyeing the eyebrows or covering them with something then drawing them with kohl; all of that is subject to the same ruling, which is that these things are permissible unless there is evidence to indicate that they are haraam. What is haraam with regard to eyebrows is plucking, but this does not come under that heading.
However, we must point out that if the substance that is used to cover the eyebrows prevents water from reaching the eyebrow, then wudoo’ is not valid unless it is removed.
And Allah knows best.