revert own fix for [#27648], looks like this needs to work differently to be fixed.

source/blender/editors/interface/interface_widgets.c

@@ -2601,6 +2601,7 @@ static void widget_box(uiBut *but, uiWidgetColors *wcol, rcti *rect, int UNUSED(
 	
 	/* store the box bg as gl clearcolor, to retrieve later when drawing semi-transparent rects
 	 * over the top to indicate disabled buttons */
+	/* XXX, this doesnt work right since the color applies to buttons outside the box too. */
 	glClearColor(wcol->inner[0]/255.0, wcol->inner[1]/255.0, wcol->inner[2]/255.0, 1.0);
 	
 	VECCOPY(wcol->inner, old_col);
@@ -2877,10 +2878,6 @@ void ui_draw_but(const bContext *C, ARegion *ar, uiStyle *style, uiBut *but, rct
 	uiFontStyle *fstyle= &style->widget;
 	uiWidgetType *wt= NULL;
 
-	/* backup the clear color [#27648], box widget clears it */
-	float clear_col[4];
-	glGetFloatv(GL_COLOR_CLEAR_VALUE, clear_col);
-
 	/* handle menus separately */
 	if(but->dt==UI_EMBOSSP) {
 		switch (but->type) {
@@ -3077,9 +3074,6 @@ void ui_draw_but(const bContext *C, ARegion *ar, uiStyle *style, uiBut *but, rct
 			if(but->dt!=UI_EMBOSSP)
 				widget_disabled(&disablerect);
 	}
-
-	/* restore clear color incase it changed */
-	glClearColor(clear_col[0], clear_col[1], clear_col[2], clear_col[3]);
 }
 
 void ui_draw_menu_back(uiStyle *UNUSED(style), uiBlock *block, rcti *rect)