gecko-dev/mobile/android/base/resources/drawable/suggestion_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_pressed="true">
        <shape>
            <gradient android:angle="90"
                      android:startColor="#E66000"
                      android:endColor="#FF9500"
                      android:type="linear"/>

            <corners android:radius="4dp"/>
        </shape>
    </item>

    <item android:state_enabled="true">
        <shape>
            <gradient android:angle="90"
                      android:startColor="#D2DAE2"
                      android:endColor="#E3E8ED"
                      android:type="linear"/>

            <corners android:radius="4dp"/>
        </shape>
    </item>

</selector>