How to edit Chrome Themes
This is a guide to help you edit your existing Chrome themes to change the default text colors and background images on New Tab page. It is fairly simple to do, and should take around 15 minutes.
You will need to have downloaded a pre-existing Chrome theme to begin. Browse the theme store to find one you like, and hit "Add to Chrome". Once you have a theme, we will want to find the folder it saves to.
Find the folder with your theme
You will need to show hidden files to see the folder. Do this by opening the Control Panel. If you're on Windows 8 or newer, the fastest way is Windows key+X, then P. Click into Appearance and Personalization, then Folder Options. Go to the View tab. There will be a list of advanced settings - we want to find the Hidden files and folders option. There should be two radio options - select the Show hidden files, folders, and drives* one. Click Apply and you're done.
Open File Explorer (Windows+x, e) and navigate to this folder. User Name shoul be replaced by your user name.
C:\Users\**User Name**\AppData\Local\Google\Chrome\User Data\Default\Extensions
Open Terminal and type
defaults write com.apple.finder AppleShowAllFiles YESto show hidden files. Navigate to
~/Library/Application Support/Google/Chrome/Default/Extensionsto find the folder containing Chrome extensions.
Open your file manager in root (
sudo nautilusin Ubuntu) and press ctrl+h to see hidden files. Navigate to
~/.config/google-chrome/Default/Extensions/to find the extensions. You could also enter into a Terminal: 'sudo vi ~/.config/google-chrome/Default/Extensions/' to edit the file directly.
Find your theme
One of these contains your theme, and the rest are other themes or extensions you have installed. Sort by Date Modified. The most recent one should be your theme, assuming this theme was the one you installed last. Open the folder, go into the version folder, and look for a file called manifest.json.
The manifest.json file is the "command center" for your theme. It controls the layout and details of your theme. Right-click it and open it with a text editor. If you're in the right folder, it'll look something like this
You'll want to be careful with what you're editing in the manifest.json file, since it controls so much, but anything within the theme subsection should be fair game. Google provides their own official documentation for theme attributes. You can change text colors by changing the RGB values associated with them.
You'll also see an images subsection in the manifest.json. Here you can specify what images will be used, and where. To change an image, you'll need to put the changes in the images folder, which can be found in the same place you found your manifest.json.
For example, if you'd rather have a different background image on the New Tab page, just rename your image
eyes.png and copy/paste it into the theme's images folder, replacing the current tab.png as you do.
If you have a .jpg you want to use instead, that's fine. Just paste it into the images folder and change the line of code in the manifest to refer to your .jpg instead. In this example, if you had an image called cat.jpg, you would change line 22 to
Confirming changes and using new theme
To see how your new theme looks, you can add it to Chrome. To do this, you'll need to enable Developer Mode. Go to Your chrome settings (chrome://extensions) and check the Developer Mode box. Click Pack extension and a window will open allowing you to select your folder. Navigate to your extension's version folder and select it.
Click OK and then you are ready to Pack Extension. You will receive a success message saying that Chrome made you a .crx and a .pem. The .crx is your new theme! Go back to that folder and double click it, opening it in Chrome. There should be a message at the bottom confirming that you want to continue adding the theme - go ahead and click continue, then OK, and that's it. Admire your new theme and give yourself a pat on the back - you just made your own awesome theme!