mastodon-ios/Mastodon/Resources/Assets.xcassets/Colors/Background/secondary.system.background.colorset/Contents.json

{
  "colors" : [
    {
      "color" : {
        "color-space" : "srgb",
        "components" : {
          "alpha" : "1.000",
          "blue" : "0x37",
          "green" : "0x2D",
          "red" : "0x29"
        }
      },
      "idiom" : "universal"
    }
  ],
  "info" : {
    "author" : "xcode",
    "version" : 1
  }
}