Add xColors API to Art & Design

README.md

@@ -197,6 +197,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Pixel Encounter](https://pixelencounter.com/api) | SVG Icon Generator | No | Yes | No |
 | [Rijksmuseum](https://data.rijksmuseum.nl/object-metadata/api/) | RijksMuseum Data | `apiKey` | Yes | Unknown |
 | [Word Cloud](https://wordcloudapi.com/) | Easily create word clouds | `apiKey` | Yes | Unknown |
+| [xColors](https://x-colors.herokuapp.com/) | Generate & convert colors | No | Yes | Yes |
 
 **[⬆ Back to Index](#index)**
 ### Authentication