Returns the alpha component of a color specification.
color
color-alpha color-spec &optional default => alpha
color-spec
A color specification.
default
A number between 0 and 1.
alpha
The alpha component of color-spec .
color-spec is a color specification in any model.
color-alpha returns the alpha component of color-spec . If color-spec does not have an alpha component, then default is returned.
color-alpha
The default value of default is 1.0.
make-hsv make-rgb make-gray