XAML in a Nutshell (In a Nutshell (OReilly))

<GradientStop Color="Yellow" Offset="0.5" />

<GradientStop .../> describes the location and Color of the transitional point in a gradient. It is used by RadialGradientBrush and LinearGradientBrush.

Attributes

Color (optional)

Describes the color of the transitional point in a gradient. The Color may be predefined in the Color class (see Appendix G) or described as a Color element. The default value is transparent.

Offset (optional)

This Double value represents the stop location in a gradient vector.