diff --git a/craft/scripts/e2e-color-system.mjs b/craft/scripts/e2e-color-system.mjs
index 79fa70d..3fd880b 100644
--- a/craft/scripts/e2e-color-system.mjs
+++ b/craft/scripts/e2e-color-system.mjs
@@ -25,7 +25,10 @@ import { buildProject } from './e2e-color-system-fixture.mjs';
 
 const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
 const BACKEND_DIR = process.env.WHP_BACKEND_DIR || '/workspace/whp-wt-color-system';
-const BASE_COMMIT = 'ab7a100';
+// Pre-colour-feature baseline. On a branch that also carries other head changes (e.g. the release
+// branch, where mobile-parity's <=767px stacking rules land first) point this at the commit just
+// before the colour merge: COLOR_BASE_COMMIT=<sha>.
+const BASE_COMMIT = process.env.COLOR_BASE_COMMIT || 'ab7a100';
 const SHOTS = process.env.COLOR_SHOTS || '';
 if (SHOTS) fs.mkdirSync(SHOTS, { recursive: true });