src/main/java/org/jfree/graphics2d/svg/SVGGraphics2D.java
private String svgColorStr() {
        String result = "black;";
        if (this.paint instanceof Color) {
            return rgbColorStr((Color) this.paint);
        } else if (this.paint instanceof GradientPaint 
                || this.paint instanceof LinearGradientPaint
                || this.paint instanceof RadialGradientPaint) {
            return "url(#" + this.gradientPaintRef + ")";
        }
        return result;
    }
private String svgColorStr() {
        String result = "black;";
        if (this.paint instanceof Color) {
            return rgbColorStr((Color) this.paint);
        } else if (this.paint instanceof GradientPaint 
                || this.paint instanceof LinearGradientPaint
                || this.paint instanceof RadialGradientPaint) {
            return "url(#" + this.gradientPaintRef + ")";
        }
        return result;
    }
Returns an SVG color string based on the current paint.  To handle
{@code GradientPaint} we rely on the {@code setPaint()} method
having set the {@code gradientPaintRef} attribute.

@return An SVG color string.