More fun than redheads? More fun than those who have taken the plunge and dyed their hair blue? I don't think so.

But I think I could make a case that Bad Grrlz who have overcome their fear of hair color have more fun than those who haven't. Changing your hair color is an act of (dare I say it?) empowerment. You have taken charge of your life and broken free of the genetic constraints.

Yes, I know the same argument could be applied to plastic surgery, but this Bad Grrl isn't going there. Cutting up my body in an effort to achieve some ideal of beauty imposed by Madison Avenue and the patriarchy. Not likely.

But I do think it's truly lovely to be able to say, "It's autumn. Maybe my hair color should change with the leaves. A nice magenta, perhaps."

So let me tell you how your hair gets its natural hair color. In your hair follicles, there are cells called melanocytes that make pigments called melanins. A hair's natural color is determined by how much and what kind of melanins are in the hair. Different melanins combine to produce the natural colors of human hair. In general, the darker the hair, the more melanin it has. As you age, the melanocytes in your hair follicles slow down or stop working altogether and your hair goes gray or white.

As millions of Bad Grrlz have discovered, modern chemistry has made it possible to color your hair for a day—or change it forever (or at least until it grows out) with a permanent tint. For the timid, there are temporary dyes, which form a colored film over each hair and wash off with shampoo.

The bolder try semipermanent dyes. These dyes contain alkali to swell and soften the layer of cuticle cells on the surface of each hair. The pigment molecules in semipermanent dyes are all small enough to sneak between the swollen cuticle cells and get inside the hairs.

Just as different natural pigments combine to make natural hair colors, a mixture of synthetic pigments blend to make a variety of colors of hair dye. A burgundy hair dye, for instance, contains both red and blue pigments. The smallest molecules, the red pigments, worm their way much deeper into the hairs than the larger molecules, the blue pigments. Over the next few weeks, some pigment molecules wash away with each shampooing. The larger molecules, which haven’t penetrated as deeply, wash away first. That’s why the color of semipermanently dyed hair fades and changes tone with each washing.

Finally, for the truly adventurous, there are chemicals that cause permanent changes to your hair: bleach and permanent dyes or tints. The solution that is used to bleach hair contains alkali to soften the cuticle cells and hydrogen peroxide to release oxygen. This oxygen penetrates your hair and reacts with the natural pigments in the cortex, the protein fibers just under the cuticle. In the cortex, oxygen breaks down the natural pigments. The bleach mixture contains modifiers to slow the release of oxygen so that the reaction happens over a period of about an hour.

After bleaching your hair to remove some of the natural pigments, you can put another color in. Permanent hair dyes start out as colorless molecules that are small enough to squeeze between the cuticle cells and get inside the hairs. These molecules react with hydrogen peroxide to become colored molecules that are too large to wash out of the hair, leaving your hair permanently colored. That’s why you can’t judge a hair color by looking at the mixture before you put it on your hair. The color of the pigments changes as the colorless molecules react with hydrogen peroxide.

At the end of a successful coloring operation, the giant pigment molecules are securely in place behind the translucent cuticle, which is once again protecting the cortex. Voila! You look wonderful.

Or maybe not. Suppose you don’t like the color and you want to change your mind. One way to get these giant molecules out of the hair is to damage the cuticle so that they fall out. Not a good idea, but people sometimes do this by mistake when they try to perm or straighten colored hair.

Another way to get the giant molecules out of the hair is with a color stripper or reducer, which reverses the action of the hydrogen peroxide, breaking the giant molecule back down into tiny molecules that can be rinsed away.

Color stripper removes the added color, but it doesn't return your hair to its natural shade. While the oxygen from the hydrogen peroxide was making giant molecules, it also destroyed some of your natural pigments. At this point, even the most adventurous should be cautious. Color stripping leaves the cuticle a little damaged so that the hair is very porous, likely to soak up any color that comes along. Trying another permanent color is risky. Some of those tiny tint molecules may still be caught inside the hair. Give them a little peroxide, and they’ll react and darken the hair again. After color stripping, it’s safest to use temporary colors while you give your hair a chance to grow out.

Sounds risky, doesn’t it? But what’s life without a little risk?