put the edit text inside a another layout and set the background colour.
So if your xml was something like this
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<EditText
android:layout_width="500dp"
android:layout_height="40dp" />
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Now it will become like
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<RelativeLayout
android:layout_width="500dp"
android:layout_height="40dp"
android:background="@color/White" >
<EditText
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
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