Eeschema plot: fix incorrect background color used to generate dimmed color.

This is for a LIB_TEXT and a SCH_FIELD.
Fixes #12709
https://gitlab.com/kicad/code/kicad/issues/12709

eeschema/lib_text.cpp

@@ -282,14 +282,14 @@ void LIB_TEXT::Plot( PLOTTER* plotter, bool aBackground, const VECTOR2I& offset,
     int      t1  = ( aTransform.x1 != 0 ) ^ ( GetTextAngle() != ANGLE_HORIZONTAL );
     VECTOR2I pos = aTransform.TransformCoordinate( txtpos ) + offset;
     COLOR4D  color = GetTextColor();
-    COLOR4D  bg = settings->GetLayerColor( LAYER_SCHEMATIC_BACKGROUND );
+    COLOR4D  bg = settings->GetBackgroundColor();
 
     if( !plotter->GetColorMode() || color == COLOR4D::UNSPECIFIED )
         color = settings->GetLayerColor( LAYER_DEVICE );
 
     if( !IsVisible() )
         bg = settings->GetLayerColor( LAYER_HIDDEN );
-    else if( !plotter->GetColorMode() )
+    else if( bg == COLOR4D::UNSPECIFIED || !plotter->GetColorMode() )
         bg = COLOR4D::WHITE;
 
     if( aDimmed )

eeschema/sch_field.cpp

@@ -965,14 +965,11 @@ void SCH_FIELD::Plot( PLOTTER* aPlotter, bool aBackground ) const
     COLOR4D          color = settings->GetLayerColor( GetLayer() );
     int              penWidth = GetEffectiveTextPenWidth( settings->GetDefaultPenWidth() );
 
-    COLOR4D bg = settings->GetLayerColor( LAYER_SCHEMATIC_BACKGROUND );
+    COLOR4D bg = settings->GetBackgroundColor();;
 
-    if( !aPlotter->GetColorMode() )
+    if( bg == COLOR4D::UNSPECIFIED || !aPlotter->GetColorMode() )
         bg = COLOR4D::WHITE;
 
-    if( SCH_SYMBOL* parent = dyn_cast<SCH_SYMBOL*>( m_parent ); parent && parent->GetDNP() )
-        color = color.Mix( bg, 0.5f );
-
     if( aPlotter->GetColorMode() && GetTextColor() != COLOR4D::UNSPECIFIED )
         color = GetTextColor();