How do I lighten colored har or dye over it? Naturally, I am almost totally gray.

If it's been colored, you must first use a color remover. There are two types of color removers: oxidizing and reducing types. The oxidizing type is mostly hair bleach (Effasol is this type). Many salons used this in the past and many still do today.

The second type of color remover, the reducing type, is sulfur-based. It uses chemicals that smell like permanent wave solutions. It reduces (in the chemical sense) the oxidized color molecules in the artificial pigment. This causes them to dissolve in water and they can be shampooed out of the hair. Products of this type include Color Zap, Color Oops, ColorFix, and Igora Phantom.

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Once the artificial pigment has been removed, your hair will almost certainly be an unpleasing yellow or orange color. This results from the hair's reaction to hydrogen peroxide when it was dyed. This is what is left of the hair's natural pigmentation. It won't go back to your natural hair color. You must re-dye it or bleach it in order to get it to a nice color. You would bleach it if your target color is more than 2 shades from your natural color or if the natural color turns too brassy when you just use an ordinary haircoloring on it.

Some people ask, "Why not simply bleach it, especially if I'm going to have to bleach it after using color remover?" The reason is that artificial pigment doesn't bleach the same as natural pigment -- and it often won't lighten past yellow or in some cases even orange. It's, therefore, important to get rid of it first.