You can find how to customize your action bar here
As for setting the values to simply be a hex, the best method to do that is to declare a colors.xml file since any colors you set to the action bar will likely be used elsewhere as well. Declaring it in xml allows for efficient reuse of the same values.
** Edit ** Here's a simple color file. It would be saved in res/values/colors.xml
<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
<color name="black_overlay">#66000000</color>
<color name="default_screen_bg">#20324a</color>
<color name="rounded_container_bg">#80000000</color>
<color name="rounded_container_border">#3b3f44</color>
<color name="light_gray_header_color">#646663</color>
</resources>