public static String colorToString(@ColorInt final int color) {
        return "R:" + Color.red(color) + ";G:" + Color.green(color) + ";B:" + Color.blue(color) + ";A:" + Color.alpha(color);
    }
Calculates contrast ratio between two {@link Color} int according to W3
<p>
See <a href="https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef">...</a>

@param rgb1 first {@link Color} int
@param rgb2 second {@link Color} int
@return contrast ratio in range from 1 to 21
main/src/main/java/cgeo/geocaching/utils/ColorUtils.java