While use fab button in android application and find difficulties to set tint color of fab button, use below code to set desire color. I have spend many hours to resolve the issue.

activity_main.xml

<com.google.android.material.floatingactionbutton.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    android:layout_gravity="bottom|end"
    app:fabSize="normal"
    app:tint="@color/colorAccent"
    app:srcCompat="@drawable/ic_google"/>