diff --git a/src/lib/order-color.ts b/src/lib/order-color.ts
new file mode 100644
index 0000000..609ece1
--- /dev/null
+++ b/src/lib/order-color.ts
@@ -0,0 +1,44 @@
+/**
+ * Per-order color helper.
+ *
+ * Hashes an order id into one of six curated Tailwind colours so each
+ * order group renders with a stable, distinct accent on list pages
+ * (Collection Confirm, Invoicing). The same id always picks the same
+ * colour across every render and every page.
+ *
+ * FNV-1a gives an even distribution with no deps. Empty / null ids
+ * fall back to the first palette entry so the helper is total.
+ */
+
+export type OrderColor = {
+  /** Left-edge stripe class, e.g. `border-emerald-500/40`. */
+  borderClass: string;
+  /** Faint body tint, e.g. `bg-emerald-500/8`. Available for callers
+   *  that want a coloured background; not used by the current pages. */
+  bgClass: string;
+};
+
+export const ORDER_COLOR_PALETTE: ReadonlyArray<OrderColor> = [
+  { borderClass: "border-emerald-500/40", bgClass: "bg-emerald-500/8" },
+  { borderClass: "border-sky-500/40", bgClass: "bg-sky-500/8" },
+  { borderClass: "border-amber-500/40", bgClass: "bg-amber-500/8" },
+  { borderClass: "border-rose-500/40", bgClass: "bg-rose-500/8" },
+  { borderClass: "border-violet-500/40", bgClass: "bg-violet-500/8" },
+  { borderClass: "border-teal-500/40", bgClass: "bg-teal-500/8" },
+];
+
+const FNV_OFFSET = 0x811c9dc5;
+const FNV_PRIME = 0x01000193;
+const PALETTE_SIZE = ORDER_COLOR_PALETTE.length;
+
+export function colorForOrder(orderId: string | undefined | null): OrderColor {
+  if (!orderId) return ORDER_COLOR_PALETTE[0];
+  let hash = FNV_OFFSET;
+  for (let i = 0; i < orderId.length; i++) {
+    hash ^= orderId.charCodeAt(i);
+    // `>>> 0` keeps the value in the uint32 range so Math.imul
+    // doesn't produce a negative result on overflow.
+    hash = Math.imul(hash, FNV_PRIME) >>> 0;
+  }
+  return ORDER_COLOR_PALETTE[hash % PALETTE_SIZE];
+}