Lemon-Aid: Great for three things 

a.) Priming a pink or purple brow before coating with the desired colour in order to turn it brown
b.) Excellent for blending into a desired pigment if a slightly lighter shade is desired
c.) By itself over a healed procedure if the colour you used is too dark. The client will leave with her brows looking slightly yellow, but they will not stay that way. In a few days the colour of the brows will not appear yellow, but they will be one or two shades lighter.

Lemon Aid