I know that this question is very old and probably the author doesn't need the answer anymore. I'll just leave it here so others can find it.
Lollipop's elevation system doesn't support colored shadows.
But, if you need colored shadows, it's possible to get them using Carbon. It's a kind-of support library for Material Design and in the most recent version there is an option to change shadow color. There's a ton of nice designs on Behance featuring colored shadows and I thought it would be nice to have them despite lack of such feature in Android. It's important to note that colored shadows are emulated on all Android versions, on 5.0+ too.
https://github.com/ZieIony/Carbon
The following image and code can be found in Carbon's samples.
Code:
<carbon.widget.LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<carbon.widget.Button
android:layout_width="56dp"
android:layout_height="56dp"
android:layout_margin="@dimen/carbon_padding"
android:background="#ffffff"
app:carbon_cornerRadius="2dp"
app:carbon_elevation="8dp"
app:carbon_elevationShadowColor="@color/carbon_red_700"/>
</carbon.widget.LinearLayout>
"CardView":
<carbon.widget.LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<carbon.widget.LinearLayout
android:layout_width="match_parent"
android:layout_height="160dp"
android:layout_margin="@dimen/carbon_margin"
android:background="#ffffff"
app:carbon_cornerRadius="2dp"
app:carbon_elevation="8dp"
app:carbon_elevationShadowColor="@color/carbon_red_700">
<carbon.widget.ImageView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:src="@drawable/test_image"/>
<carbon.widget.TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="test text"/>
</carbon.widget.LinearLayout>
</carbon.widget.LinearLayout>
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