rgba Expression To Color String
Convert an rgba or rgb Expression to a rgba(...)
String.
R, G, B color components have to be in the [0-255]
range, while alpha has to be in the [0.0-1.0]
range. For example: "rgba, 255, 128, 0, 0.7".
Return
the String representation of rgba
Parameters
value
the Expression representation of rgba/rgb