Had the same problem, was able to fix it manually:

go to src-capacitor/android/app/src/main/res/values/ic_launcher_background.xml ic_launcher_background.xml content should look like:

<?xml version=“1.0” encoding=“utf-8”?>
<resources>
<color name=“ic_launcher_background”>#0062A0</color>
</resources>

just change color code in the <color>!

@aitcheyejay , can you share the hack?