Get darker color hex code for given color hex code

Question

How to get darker color hex code for the given color(represented with hex code).

For example, for given color #999999 i want to get darker hex color, namely it can be #666666, because #666666 is darker than #999999, and they are GREY

Another example, for given orange color, I want to get darker orange color hex code.

Assume we use ActionScript 3.

Answer 1

Depending on what you are after, you may have better results by working with the HSL color space and adjusting the L value. This is what the color picker in the Flash authoring tool does when you lighten/darken a color. A little Googling will dig up the forumlas and code for converting RGB to HSL and vice versa.