Theming your android app might be quite of a task if you don't have an eye for design and color combination. It's much easier when you are placed on a project that has designs created by a UI/UX designer.
A theme is applied throughout the entire app, not just a single view. Theming your app includes creating a color scheme for it. An android app's color scheme is made up of a primary color,or sometimes a combination of the primary color and secondary color.

Primary Color
The primary color is the color that the user will see on the screen and on your app's components the most. The primary color will appear on your appbar, status bar, and tabview for example.

Secondary Color
The secondary color can be used to emphasize the different components on the screen. The secondary color can be used on floating action buttons, progress bars, or switches for example.

Side Note:
It is not always required to have a secondary color. The app can use the primary color's variants as it's secondary color. Primary color variants are the lighter and darker shades of the color.

So how do we tackle the task of theming our apps? Fortunately for android beginners, Material Design has a cool color palette tool, called Color Tool.

The Color Tool helps you visualize how your app would look like with the colors you would choose.
The tool also allows you to export the color xml and just paste it in your android colors.xml file.
You simply click on the Export button on the top right side of the website, it will then download your scheme as an xml file. You then simply copy the text from the xml file to your color.xml file of your Android project, as shown below:

Another awesome tool is the Material Design Palette, which also provides a visualization of the theme. You can simply click on the download button to get the xml version of the scheme, and then just simply copy and paste it into your colors.xml file.

With the tools made available, it is now easier to style your app. Some useful resources:
-Material Design
-Android Developer Guidelines

Need some insipiration? Check out what other developers and designers are crafting on UpLabs.

Credits:
Cover Image - A big thank you to Markus Spiske, taken from Unsplash