Create another XML file in res\color named something like text_color.xml (based on Adil Soomro's answer here):
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<!-- disabled state -->
<item android:state_enabled="false" android:color="#000000" />
<item android:color="#FFFFFF"/>
</selector>
In your style.xml, replace
<item name="android:textColor">#FFFFFF</item>
to
<item name="android:textColor">@color/text_color</item>