android theme using multiple colors.xml

I am new to android development, so please bear with me. My app elements (button color, background color, text color, divider color etc.) uses colors from the colors.xml using "@color/mycolor" for example.

My colors.xml looks like:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="mycolor">#202020</color>
    <color name="white">#FFFFFF</color>
    <color name="whitehint">#50FFFFFF</color>
    <color name="primary">#673AB7</color>
    <color name="primary_dark">#512DA8</color>
    <color name="primary_light">#D1C4E9</color>
    <color name="accent">#794cc9</color>
    <color name="primary_text">#212121</color>
    <color name="secondary_text">#a4a4a4</color>
    <color name="icons">#FFFFFF</color>
    <color name="divider">#B6B6B6</color>
</resources>

Now I have a menu where the user can select a different theme which I want to use a second colors2.xml for example which will have the same color names but a different hex code for the keys. How do I go about which xml file does my app references?