src/main/java/org/jfree/graphics2d/svg/SVGGraphics2D.java
private String rgbaColorStr(Color c) {
        StringBuilder b = new StringBuilder("rgba(");
        double alphaPercent = c.getAlpha() / 255.0;
        b.append(c.getRed()).append(",").append(c.getGreen()).append(",")
                .append(c.getBlue());
        b.append(",").append(transformDP(alphaPercent));
        b.append(")");
        return b.toString();
    }
private String rgbaColorStr(Color c) {
        StringBuilder b = new StringBuilder("rgba(");
        double alphaPercent = c.getAlpha() / 255.0;
        b.append(c.getRed()).append(",").append(c.getGreen()).append(",")
                .append(c.getBlue());
        b.append(",").append(transformDP(alphaPercent));
        b.append(")");
        return b.toString();
    }
Returns a string representing the specified color in RGBA format.

@param c  the color ({@code null} not permitted).

@return The SVG RGBA color string.