If you do bleach, be very careful with it that close to the eye.
For a temporary basis, there are a number of methods, including mascaras, glue and paint, and theatrical hair paints designed specifically for that sort of thing. These
are my preferred method; Not a great shot, but here's how it looks
when taking very dark eyebrows grey. (We weren't going for full white, but it gives pretty darned good coverage.)