diff --git a/packages/codex-plugin/.codex-plugin/plugin.json b/packages/codex-plugin/.codex-plugin/plugin.json
index a21ebe5..eae1474 100644
--- a/packages/codex-plugin/.codex-plugin/plugin.json
+++ b/packages/codex-plugin/.codex-plugin/plugin.json
@@ -35,7 +35,8 @@
       "Read"
     ],
     "websiteURL": "https://judgmentkit.ai",
-    "brandColor": "#255C99",
+    "brandColor": "#0B0D0E",
+    "brandColorDark": "#F7F6F2",
     "defaultPrompt": [
       "Make a first UI pass from this brief. Infer what you can, show the working premise and key decisions, and ask only if a missing decision would materially change the design.",
       "Turn this sanitized Figma or generated screen into a reviewed activity case and implementation handoff.",
diff --git a/scripts/verify-codex-plugin.mjs b/scripts/verify-codex-plugin.mjs
index 0909b99..1ff9791 100644
--- a/scripts/verify-codex-plugin.mjs
+++ b/scripts/verify-codex-plugin.mjs
@@ -18,6 +18,12 @@ export const DEFAULT_CANONICAL_SKILL_DIR = path.join(
 export const CODEX_PLUGIN_MCP_URL = "https://judgmentkit.ai/mcp";
 export const STRICT_BASE_SEMVER_PATTERN = /^\d+\.\d+\.\d+$/;
 
+// Approved Ink/Ivory palette in brand/slab-j/README.md.
+const CANONICAL_PLUGIN_COLORS = {
+  brandColor: "#0B0D0E",
+  brandColorDark: "#F7F6F2",
+};
+
 export const PORTABLE_SKILL_FILES = [
   "SKILL.md",
   "references/ui-handoff-and-acceptance.md",
@@ -395,6 +401,16 @@ function collectMissingWordingFailures({ skillText, uiReferenceText, deckReferen
 function collectManifestFailures(pluginJson) {
   const failures = [];
 
+  for (const [field, expected] of Object.entries(CANONICAL_PLUGIN_COLORS)) {
+    if (pluginJson?.interface?.[field] !== expected) {
+      failures.push({
+        check: "canonical_brand_colors",
+        file: ".codex-plugin/plugin.json",
+        message: `Plugin manifest interface.${field} must use canonical color ${expected}.`,
+      });
+    }
+  }
+
   if (pluginJson?.name !== "judgmentkit") {
     failures.push({
       check: "plugin_manifest",
diff --git a/tests/codex-plugin.test.mjs b/tests/codex-plugin.test.mjs
index d8d7378..4928250 100644
--- a/tests/codex-plugin.test.mjs
+++ b/tests/codex-plugin.test.mjs
@@ -69,6 +69,8 @@ async function createFixture(overrides = {}) {
       category: "Productivity",
       capabilities: ["Interactive", "Read"],
       websiteURL: "https://judgmentkit.ai",
+      brandColor: "#0B0D0E",
+      brandColorDark: "#F7F6F2",
       defaultPrompt:
         overrides.pluginDefaultPrompt ??
         ["Make a first UI pass, show the working premise, and ask only if a missing decision would materially change the design."],
@@ -190,6 +192,22 @@ for (const phrase of [
   assert.ok(result.files_checked.includes("skills/judgmentkit-hosted-mcp/agents/openai.yaml"));
 }
 
+for (const field of ["brandColor", "brandColorDark"]) {
+  for (const value of [undefined, "#255C99"]) {
+    const fixture = await createFixture();
+    const manifestPath = path.join(fixture.sourceDir, ".codex-plugin", "plugin.json");
+    const manifest = await readJson(manifestPath);
+    if (value === undefined) delete manifest.interface[field];
+    else manifest.interface[field] = value;
+    await writeJson(manifestPath, manifest);
+
+    await assertVerifyRejects(
+      { sourceDir: fixture.sourceDir, packageJsonPath: fixture.packageJsonPath },
+      ["canonical_brand_colors"],
+    );
+  }
+}
+
 {
   const fixture = await createFixture({ pluginVersion: "1.2.4" });
   await assertVerifyRejects(