some colors are just not in colors.xml they are defined in layout files , as atomant247 has shown above , not that common but
I know certain apps will use this method especially if the APK has been updated and the dev wants to add something different he will use the layout files sometimes.
Point to note for future reference ,look for an app named DEV ASSISTANT
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Its free and what it does is when an app is running you can call up an xray screen that lets you point to areas or button on the screen and it
shows you in text output what/where files each item are in the apk, cuts a lot of time off like for instance the top bar of the EPG guide , if you had run the dev assistant it would first tell you the name of the bar inside the apk and the color value it will also tell you which files you need to edit.
easy when you know how , point to note does not work to well on an emulator but on a tablet or phone works great , bit fiddly to use but worth the effort.