The opacity of the color from 0.0 for completely translucent to 1.0 for opaque
The intensity of the blue channel from 0.0 to 1.0 inclusive
The intensity of the green channel from 0.0 to 1.0 inclusive
The intensity of the red channel from 0.0 to 1.0 inclusive
A gdk.rgba.RGBA is used to represent a color, in a way that is compatible with cairo’s notion of color.
gdk.rgba.RGBA is a convenient way to pass colors around. It’s based on cairo’s way to deal with colors and mirrors its behavior. All values are in the range from 0.0 to 1.0 inclusive. So the color (0.0, 0.0, 0.0, 0.0) represents transparent black and (1.0, 1.0, 1.0, 1.0) is opaque white. Other values will be clamped to this range when drawing.