diff --git a/schemas/entity-styles.json b/schemas/entity-styles.json
index 03a0516..7d6f5a5 100644
--- a/schemas/entity-styles.json
+++ b/schemas/entity-styles.json
@@ -1,8 +1,55 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "title": "Entity Styles",
-  "type": "object",
   "definitions": {
+    "styles": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "thumbnail": {
+          "$ref": "#/definitions/image"
+        },
+        "hero": {
+          "$ref": "#/definitions/image"
+        },
+        "background": {
+          "$ref": "#/definitions/color"
+        },
+        "text": {
+          "$ref": "#/definitions/color"
+        },
+        "style_modes": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+              "mode": { "type": "string" },
+              "styles": { "$ref": "#/definitions/nestedStyles" }
+            },
+            "required": ["mode", "styles"]
+          }
+        }
+      }
+    },
+    "nestedStyles": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "thumbnail": {
+          "$ref": "#/definitions/image"
+        },
+        "hero": {
+          "$ref": "#/definitions/image"
+        },
+        "background": {
+          "$ref": "#/definitions/color"
+        },
+        "text": {
+          "$ref": "#/definitions/color"
+        }
+      }
+    },
     "image": {
       "type": "object",
       "properties": {
@@ -27,18 +74,16 @@
       "required": ["color"]
     }
   },
-  "properties": {
-    "thumbnail": {
-      "$ref": "#/definitions/image"
-    },
-    "hero": {
-      "$ref": "#/definitions/image"
-    },
-    "background": {
-      "$ref": "#/definitions/color"
-    },
-    "text": {
-      "$ref": "#/definitions/color"
+  "oneOf": [
+    { "$ref": "#/definitions/styles" },
+    {
+      "type": "object",
+      "minProperties": 1,
+      "additionalProperties": false,
+      "properties": {
+        "light": { "$ref": "#/definitions/styles" },
+        "dark": { "$ref": "#/definitions/styles" }
+      }
     }
-  }
+  ]
 }
diff --git a/spec/spec.md b/spec/spec.md
index fc07799..b7cfa8f 100644
--- a/spec/spec.md
+++ b/spec/spec.md
@@ -56,8 +56,9 @@ _Entity Style Descriptors_ are a resource format that defines a set of suggested
 ```
 :::
 
+An _Entity Style Descriptor_ ****must**** be an object composed in one of the follow ways:
 
-An _Entity Style Descriptor_ ****must**** be an object composed of the following properties:
+### Basic
 
 - The object ****MAY**** contain a `thumbnail` property, and if present, its value ****MUST**** be an object with the following optional properties:
     - The object ****MUST**** contain a `uri` property, and if present its value ****MUST**** be a valid URI string to an image resource.
@@ -69,6 +70,35 @@ An _Entity Style Descriptor_ ****must**** be an object composed of the following
     - The object ****MAY**** contain a `color` property, and if present its value ****MUST**** be a HEX string color value (e.g. #000000).
 - The object ****MAY**** contain a `text` property, and if present, its value ****MUST**** be an object with the following optional properties:
     - The object ****MAY**** contain a `color` property, and if present its value ****MUST**** be a HEX string color value (e.g. #000000).
+- The object ****MAY**** contain a `style_modes` property, and if present, its value ****MUST**** be an array of [ref:Style Mode Objects].
+
+### Light and Dark Mode
+
+::: example Light and Dark Mode
+```json
+[[insert: ./test/entity-styles/simple-light-dark.json]]
+```
+:::
+
+- The object ****MAY**** contain `light` and/or `dark` properties, and if present, their values ****MUST**** be Basic Entity Style Descriptors
+
+## Entity Style Modes
+
+::: example Modes
+```json
+[[insert: ./test/entity-styles/simple-light-dark.json]]
+```
+:::
+
+A _Entity Style Mode_ ****must**** be an object composed of the following properties:
+
+- The object ****MUST**** contain a `mode` property and its value ****MUST**** be a string
+  - This string ****MUST**** be unique within the containing `style_modes` array
+- The object ****MUST**** contain a `styles` property and its value ****MUST**** be a [ref:Entity Style Descriptor] omitting the `style_modes` property
+
+### Applying Modes
+
+When a style mode its `styles` property ****MUST**** be merged with its containing [ref:Entity Style Descriptor]
 
 ## Data Display
 
diff --git a/test/entity-styles/modes.json b/test/entity-styles/modes.json
new file mode 100644
index 0000000..598b12e
--- /dev/null
+++ b/test/entity-styles/modes.json
@@ -0,0 +1,44 @@
+{
+  "light": {
+    "thumbnail": {
+      "uri": "https://dol.wa.com/logo.png",
+      "alt": "Washington State Seal"
+    },
+    "hero": {
+      "uri": "https://dol.wa.com/people-working.png",
+      "alt": "People working on serious things"
+    },
+    "background": {
+      "color": "#ff0000"
+    },
+    "text": {
+      "color": "#d4d400"
+    },
+    "style_modes": [
+      {
+        "mode": "red-green-color-blind",
+        "styles": {
+          "background": {
+            "color": "#800080"
+          }
+        }
+      }
+    ]
+  },
+  "dark": {
+    "thumbnail": {
+      "uri": "https://dol.wa.com/logo-alt.png",
+      "alt": "Washington State Seal"
+    },
+    "hero": {
+      "uri": "https://dol.wa.com/people-working-alt.png",
+      "alt": "People working on serious things"
+    },
+    "background": {
+      "color": "#00FFFF"
+    },
+    "text": {
+      "color": "#0000D4"
+    }
+  }
+}
diff --git a/test/entity-styles/simple-light-dark.json b/test/entity-styles/simple-light-dark.json
new file mode 100644
index 0000000..49afe3e
--- /dev/null
+++ b/test/entity-styles/simple-light-dark.json
@@ -0,0 +1,34 @@
+{
+  "light": {
+    "thumbnail": {
+      "uri": "https://dol.wa.com/logo.png",
+      "alt": "Washington State Seal"
+    },
+    "hero": {
+      "uri": "https://dol.wa.com/people-working.png",
+      "alt": "People working on serious things"
+    },
+    "background": {
+      "color": "#ff0000"
+    },
+    "text": {
+      "color": "#d4d400"
+    }
+  },
+  "dark": {
+    "thumbnail": {
+      "uri": "https://dol.wa.com/logo-alt.png",
+      "alt": "Washington State Seal"
+    },
+    "hero": {
+      "uri": "https://dol.wa.com/people-working-alt.png",
+      "alt": "People working on serious things"
+    },
+    "background": {
+      "color": "#00FFFF"
+    },
+    "text": {
+      "color": "#0000D4"
+    }
+  }
+}