I know its too late to answer this question but still posting my answer here so that others can have reference:
<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
android:height="100dp"
android:width="100dp"
android:viewportHeight="100"
android:viewportWidth="100">
<path
android:name="dark_triangle"
android:fillColor="#FFFFFF"
android:pathData="M 100,0 L 0,100 100,100 z" />
<path
android:name="light_triangle"
android:fillColor="#d0021b"
android:pathData="M 0,0 L 100,0 0,100 z" />
</vector>