How to reskin game GUI in Unity

1. Go to Assets -> Resources -> Popups

   
2. Choose the UI that you want to modify. For example, let's select the Settings UI

3. Look in the Inspector

4. Select Menus_label Source Image

   
5. Change the color to the one you want

   
6. Repeat the process for other images, buttons, and text elements

   
7. Use the eyedropper tool (pipette) to pick a color from any image or reference

   
8. To change the background, reskin the main-background.png file. You can find it in the Sprites -> general-ui folder. The background is a gradient, so to reskin it, you'll need to use a graphic editor.