balloon has white background

[theapache64]

Below given my Seekbar

<com.xw.repo.BubbleSeekBar
                    android:id="@+id/bsb_frequency"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    app:bsb_max="5"
                    app:bsb_section_count="5"
                    app:bsb_min="0"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintStart_toStartOf="@id/tv_label_frequency"
                    app:layout_constraintTop_toBottomOf="@id/tv_label_frequency" />

and the balloon shows white background.

• Why the balloon has white background and how do I remove it ?