How to change the ink colour and size of the pen tool in the slideshow of Microsoft PowerPoint in Android version?

I have Microsoft office paid account. And it's for Android. So I am using it in my samsung tablet. I am using it for teaching purpose, so I must use the pen tool in slideshow. But the pen tool in slideshow gives me fixed colour. There is no choice in choosing the multiple colours. And there is also the fixed weight of the pen. **I want to use multiple colours and want to make my pen thicker by increasing its thickness. But there is no option in it.** How can I do that?