Создаём *drawable* ресурс с типом *shape*

```xml
<?xml version="1.0" encoding="utf-8"?>
<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners
        android:radius="40dp">
    </corners>
    <solid
        android:color="#00FF00">
    </solid>
</shape>
```
