How to set the background resource of a button from one custom drawable to another custom drawable in kotlin?

I have a set of buttons in Android which all use the same custom drawable as the background, When a button is pressed, I'd like the drawable that is used for the background to change to a different custom drawable. The code I used to do this is below:

selectedButton.setBackgroundResource(R.drawable.roundedbuttongreen) // Change the background resource to the roundedbuttongreen drawable

the XML for the custom drawable called roundedbuttongreen.xml is:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" android:padding="10dp">
    <solid android:color="#4CAD71"/> <!-- this one is ths color of the Rounded Button -->
    <corners
            android:bottomLeftRadius="50dp"
            android:bottomRightRadius="50dp"
            android:topLeftRadius="50dp"
            android:topRightRadius="50dp"/>
</shape>

The problem that occurs is that the colour of the button is changed but not to the correct colour the colour it changes to instead is grey, it should be green. The screenshot is below:

image of the button after the background resource has been changed, it should be green

If anyone could let me know what I'm doing wrong that would be great

Solution

I had a look through my xml code for my layout and in particular my buttons, The issue was that the buttons backgroundTint property had a value which was grey, as a result when I tried to change the background drawable, the colour of the button was always grey.

To fix the issue, I changed the value of the background tint to green and the issue was resolved