Examine source code of Sandfell

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#a0c2cb",
      "tab_background_text": "#747055"
    }
  },
  "version": "2.0",
  "name": "Sandfell",
  "manifest_version": 2,
  "description": "The first theme I design in Firefox dev.ed.\nThe mountain Sandfell is close to my home where we had sheeps."
}