diff --git a/src/app.cpp b/src/app.cpp
index d7b6c9e..6e4b0f1 100644
--- a/src/app.cpp
+++ b/src/app.cpp
@@ -2804,7 +2804,9 @@ static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bo
         const float pct = std::clamp((float)cur / (float)tipHeight, 0.0f, 1.0f);
 
         // Track + accent fill up to the thumb (fill's rounded right edge matches the thumb circle).
-        dl->AddRectFilled(barMin, barMax, IM_COL32(255, 255, 255, enabled ? 26 : 12), barRound);
+        // OnSurface-based (not pure white) so the track/label/thumb stay visible on a light-theme glass
+        // panel, which goes opaque white.
+        dl->AddRectFilled(barMin, barMax, m::WithAlpha(m::OnSurface(), enabled ? 30 : 14), barRound);
         const float usableW = barW - thumbR * 2.0f;
         const float thumbCenterX = barMin.x + thumbR + usableW * pct;
         const float fillRight = thumbCenterX + thumbR;
@@ -2820,13 +2822,13 @@ static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bo
             const ImVec2 tsz = cap->CalcTextSizeA(cap->LegacySize, 10000.0f, 0.0f, pctBuf);
             dl->AddText(cap, cap->LegacySize,
                         ImVec2(barMin.x + (barW - tsz.x) * 0.5f, barMin.y + (barH - tsz.y) * 0.5f),
-                        IM_COL32(255, 255, 255, enabled ? 190 : 80), pctBuf);
+                        m::WithAlpha(m::OnSurface(), enabled ? 200 : 80), pctBuf);
         }
 
         // Glass thumb (drawn last so it sits above the fill + label).
         const float thumbY = barMin.y + barH * 0.5f;
-        dl->AddCircleFilled(ImVec2(thumbCenterX, thumbY), thumbR, IM_COL32(255, 255, 255, enabled ? 205 : 90), 24);
-        dl->AddCircle(ImVec2(thumbCenterX, thumbY), thumbR, IM_COL32(255, 255, 255, enabled ? 120 : 50), 24, 1.4f * dp);
+        dl->AddCircleFilled(ImVec2(thumbCenterX, thumbY), thumbR, m::WithAlpha(m::OnSurface(), enabled ? 215 : 90), 24);
+        dl->AddCircle(ImVec2(thumbCenterX, thumbY), thumbR, m::WithAlpha(m::OnSurface(), enabled ? 130 : 50), 24, 1.4f * dp);
 
         if (hovered && enabled) {
             ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);