presto-main/src/main/java/io/prestosql/operator/scalar/ColorFunctions.java/ColorFunctions/bar
class ColorFunctions:    @ScalarFunction
    @SqlType(StandardTypes.VARCHAR)
    public static Slice bar(@SqlType(StandardTypes.DOUBLE) double percent, @SqlType(StandardTypes.BIGINT) long width)
    {
        return bar(percent, width, rgb(255, 0, 0), rgb(0, 255, 0));
    }