How do I sort colors in the color table in photoshop

I'm using adobe photoshop cs version 8.0.

Using the menu: Image > Mode > Color Table, I'm trying to make some colors transparent.

The problem is that the range of colors I need to pick is scattered all over the color table. How do I sort the colors in the color table according to saturation to ease my work?

In the picture below, the background should be transparent so that only the lady's face and hair should be extracted.