message: Change date-time string formats and color properties to use regex
diff: "anyOf": [
  {"type": "number"},
  {"type": "string"},
  - {
  - "type": "string",
  - "format": "date-time"
  - }
  + {"$ref": "#/definitions/w3cDate"}
  ],
  "examples": ["<a href='http://example.com/customers/123'>Edit my profile</a>"]
  },
  {"type": "number"},
  {"type": "string"},
  {
  - "type": "string",
  - "format": "date-time"
  + "$ref": "#/definitions/w3cDate"
  }
  ],
  "examples": [42]
  "expirationDate": {
  "title": "Expiration Date",
  "description": "Date and time when the pass expires.\nAvailable in iOS 7.0.",
  - "type": "string",
  - "format": "date-time"
  + "$ref": "#/definitions/w3cDate"
  },
  "voided": {
  "title": "Voided",
  "relevantDate": {
  "title": "Relevant Date",
  "description": "Date and time when the pass becomes relevant. For example, the start time of a movie.\nRecommended for event tickets and boarding passes.",
  - "type": "string",
  - "format": "date-time"
  + "$ref": "#/definitions/w3cDate"
  },
  "boardingPass": {
  "title": "Boarding Pass",
  "backgroundColor": {
  "title": "Background Color",
  "description": "Background color of the pass, specified as an CSS-style RGB triple.",
  - "type": "string",
  + "$ref": "#/definitions/color",
  "examples": ["rgb(23, 187, 82)"]
  },
  "foregroundColor": {
  "title": "Foreground Color",
  "description": "Foreground color of the pass, specified as a CSS-style RGB triple",
  - "type": "string",
  + "$ref": "#/definitions/color",
  "examples": ["rgb(100, 10, 110)"]
  },
  "groupingIdentifier": {
  "labelColor": {
  "title": "Label Color",
  "description": "olor of the label text, specified as a CSS-style RGB triple.\nIf omitted, the label color is determined automatically.",
  - "type": "string",
  + "$ref": "#/definitions/color",
  "examples": ["rgb(255, 255, 255)"]
  },
  "logoText": {
  