diff --git a/frontend/css/styles.css b/frontend/css/styles.css
index f580eaa..fe716b3 100644
--- a/frontend/css/styles.css
+++ b/frontend/css/styles.css
@@ -728,7 +728,7 @@ select {
 /* HR on/off toggle on the record screen (replaces the wind button): grey = off, coloured = on. */
 .rec-hr-toggle { color: #888; display: inline-flex; align-items: center; justify-content: center; gap: 3px; padding: 6px 10px; }
 .rec-hr-toggle svg { display: block; }
-.rec-hr-toggle.active { color: #ef5350; background: rgba(239, 83, 80, 0.18); }
+.rec-hr-toggle.active { color: #fff; background: #ef5350; } /* on = white icon+bpm on solid red */
 .rec-hr-num { font-size: 14px; font-weight: 700; min-width: 0; }
 .rec-hr-num:empty { display: none; }