With Windows Phone 8.1, you can now choose any background images for your Start screen tiles. A nice side effect of this is that you can now also put custom colors for your live tiles too! No, Windows Phone 8.1 did not add new accent colors for you to customize device with. Instead, you can use a solid color of your choice as the background picture for your tiles!
Use Good Old Paint
One way you can use custom colors is using Microsoft Paint built into all Windows operating system. Just open paint, and use the color bucket tool to fill the page with a color of your choice. Save the file to your OneDrive cloud storage or directly to your phone’s pictures folder by connecting your phone to your PC.
From your Phone, go to Settings and choose “Start + Themes”. Then, tap “Choose Photo” button. Select your photo either from OneDrive or your phone, depending on where you saved the picture.
Voila! You are done! You are now rocking a custom color for your tiles. Enjoy!
Use an App
Alternatively, you can download an application from the Windows Phone Store to do all the hard work for you. WPCentral found an app that does just that. Simply run the app, choose your color and save the image containing the solid color.

Download the app here.
Then, go to your phone’s Settings app and choose “Start + Themes”. Then, tap “Choose Photo” button. Select your photo either from OneDrive or your phone, depending on where you saved the picture.
Voila! You are done! You are now rocking a custom color for your tiles. Enjoy!