Index: indra/llui/llbutton.cpp
===================================================================
--- indra/llui/llbutton.cpp	(revision 90254)
+++ indra/llui/llbutton.cpp	(revision 90255)
@@ -476,8 +476,8 @@
 	{
 		use_glow_effect = TRUE;
 		glow_type = LLRender::BT_ALPHA; // blend the glow
-		if (mNeedsHighlight) // highlight color takes precedence
-			glow_color = glow_color % 0.5; // ... but less opaque.
+		if (mNeedsHighlight) // highlighted AND flashing
+			glow_color = (glow_color*0.5f + mFlashBgColor*0.5f) % 2.0f; // average between flash and highlight colour, with sum of the opacity
 		else
 			glow_color = mFlashBgColor;
 	}