@NRowe I prefer the lighter/red tone. If you wanted to you could leave the eyebrows in the original brown tone as to indicate that the hair is colour treated. But it is most important that you have fun with your "challenge". I personally find it difficult to break out of patterns, but sometimes it is very rewarding. For me it was when I played an evil Snob with the 'Public Enemy' aspiration or a sim with the 'Serial Romantic' aspiration. Have completed both of these only once so far, because they contradict my usual playstyle, but it was a fun way to mix things up.
