Vfrdtyky

I added a FloatingActionButton in the layout where its only parent is a CoordinatorLayout, so I don't understand where the backgroundTint color is coming from.

I tried to change the color to match the inner circle, but it changes the whole button to a solid color.

I also applied a different style, but it does not change the button at all.
I fixed this problem in the past, but I don't remember how I did it.

<android.support.design.widget.FloatingActionButton

        android:id="@+id/fab"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_margin="16dp"

        android:src="@drawable/ic_action_add"

        app:layout_anchor="@+id/edit_layout"

        app:layout_anchorGravity="bottom|right|end" />

The gray color comes from your colorAccent defined for the app theme in style.xml. Now the @drawable/ic_action_add is a plus sign inside a filled circle. Try to use below icon instead:

ic_add_black_24dp.xml

<vector xmlns:android="http://schemas.android.com/apk/res/android"

    android:width="24dp"

    android:height="24dp"

    android:viewportWidth="24.0"

    android:viewportHeight="24.0">

    <path

        android:fillColor="#000000"

        android:pathData="M19,13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z" />

</vector>

Then set a crimson color to the FloatingActionButton's background tint and the gray one for icon tint:

<android.support.design.widget.FloatingActionButton

    android:id="@+id/fab"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:layout_gravity="bottom|end"

    android:layout_margin="16dp"

    app:layout_anchor="@+id/edit_layout"

    app:layout_anchorGravity="bottom|right|end"

    app:tint="#404D54"

    app:backgroundTint="#6F303A"

    app:srcCompat="@drawable/ic_add_black_24dp" />

Result:

You are not providing any app:backgroundTint, so it is using the default colorAccent from colors.xml.

To solve this:

1.Add a new color to colors.xml

<color name="fab_tint">#33d1ac</color>

2.Change the code as follows:

  <android.support.design.widget.FloatingActionButton

    android:id="@+id/fab"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:layout_margin="16dp"

    android:src="@drawable/ic_action_add"

    app:layout_anchor="@+id/edit_layout"

    app:layout_anchorGravity="bottom|right|end"         

    app:backgroundTint="@color/fab_tint"/>