gdk-rgba-new (&key red green blue alpha)

red -- the double float intensity of the red channel from 0.0 to 1.0 inclusive
green -- the double float intensity of the green channel from 0.0 to 1.0 inclusive
blue -- the double float intensity of the blue channel from 0.0 to 1.0 inclusive
alpha -- the double float opacity of the color from 0.0 for completely translucent to 1.0 for opaque

Creates a gdk-rgba color.