//Add this to your button xml element
android:background="@android:color/[INSERT_COLOR]"
//You might have to change the text color to make the text readable
//Change this line in both of the themes.xml files
<style name="Theme.[INSERT_APP_NAME]" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
//to
<style name="Theme.[INSERT_APP_NAME]" parent="Theme.AppCompat.DayNight.NoActionBar">
// you can change the .NoActionBar to light action bar or dark action bar if you want to