This command initiates a dialog that allows the user to specify two colors: the High Color and the Low Color to be used for the sky gradient colors.  The program uses these two colors to create a smooth range of colors that will stretch from top of the image at the high range to the horizon at the lowat the high range.   Clicking on the box representing either the  High Color or the Low Color will bring up the standard ColorPicker allowing the user to select the desired color.  These colors are used to pre-fill the portion of the image area above the horizon before doing a polygon fill.

The user also has the choice of either an HSV space gradient or an RGB space gradient.  This allows for a wider range of effects.  RGB space gradients are the default.

When running on 8-bit color (or any clut type display), Fractal! will set the color palette to the most appropriate one for the 32-bit  image  just rendered.