Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A

On the left side of the page, select Themes.

Sorry, should have been more specific, I meant where the actual files are kept, like the directory not in firefox.

Do you want to edit the image files? In your profile folder, these are the most recent:

• lightweighttheme-header
• lightweighttheme-footer

(I don't know what happens to the previously used theme image files.)

These do not have .png file extensions, but I'm pretty sure they are PNG files. You could rename them if necessary to get your image editing software to open them, then rename them back so Firefox can find them.

If you wanted to modify the text or accent colors of the theme, they are stored in the prefs.js file and can be viewed/modified in about:config as follows.

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste theme and pause while the list is filtered

(3) Right-click > Copy Value on the lightweightThemes.usedThemes preference and you can paste it somewhere more convenient to view such parameters as the

• "textcolor":"#ffffff"
• "accentcolor":"#1a2446"

In theory you could modify those values and paste the whole string of data back in, but I haven't tried it myself.

Note that you may have to delete the lwthemes folder because this folder stores the actual images in the required dimensions that Firefox uses.

Note that Firefox uses lightweightThemes.selectedThemeID to specify which of the available themes is used.