diff --git a/frontend/src/lib/consts.ts b/frontend/src/lib/consts.ts
index db111d9..e01f565 100644
--- a/frontend/src/lib/consts.ts
+++ b/frontend/src/lib/consts.ts
@@ -124,6 +124,24 @@ export const DENSITY_GRADIENT_DARK: { t: number; color: [number, number, number]
   { t: 1, color: [255, 170, 40] },
 ];
 
+/**
+ * Hexagons & postcodes filtered out by the active filters (count <= 0) stay on
+ * the map as faint grey "ghosts": de-emphasised but still visible and clickable,
+ * so users can tell something is there without it competing with the matching
+ * results. Tuned to read as subtle against both the light and dark basemaps.
+ */
+export const FILTERED_OUT_FILL: Record<'light' | 'dark', [number, number, number, number]> = {
+  light: [150, 150, 150, 45],
+  dark: [120, 114, 108, 50],
+};
+
+/** Border for a filtered-out postcode — a touch stronger than its fill so the
+ *  polygon outline stays legible. */
+export const FILTERED_OUT_LINE: Record<'light' | 'dark', [number, number, number, number]> = {
+  light: [110, 110, 110, 80],
+  dark: [150, 145, 140, 70],
+};
+
 /** Protomaps font glyphs URL (served locally from public/assets/) */
 export const GLYPHS_URL = '/assets/fonts/{fontstack}/{range}.pbf';