Examine source code of Harbour

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#e3b505",
      "tab_background_text": "#313e47"
    }
  },
  "version": "2.0",
  "name": "Harbour",
  "manifest_version": 2,
  "description": "I'm making series of Firefox Themes using contrasting colors on tool bar & tab bar. Despite the limitation of the setting one universal text color, I'll try my best to seek for the best contrasting tones on Firefox. \n\nThis theme is dedicated to the harbour of my home city - Victoria Harbour."
}