diff --git a/src/widget.cpp b/src/widget.cpp
--- a/src/widget.cpp
+++ b/src/widget.cpp
@@ -282,10 +282,10 @@ void DrawFrameRect(int left, int top, in
 {
 	assert(colour < COLOUR_END);
 
-	uint dark         = GetColourGradient(colour, SHADE_3);
-	uint medium_dark  = GetColourGradient(colour, SHADE_5);
-	uint medium_light = GetColourGradient(colour, SHADE_6);
-	uint light        = GetColourGradient(colour, SHADE_7);
+	uint dark         = GetColourGradient(colour, SHADE_DARK);
+	uint medium_dark  = GetColourGradient(colour, SHADE_LIGHT);
+	uint medium_light = GetColourGradient(colour, SHADE_LIGHTER);
+	uint light        = GetColourGradient(colour, SHADE_LIGHTEST);
 
 	if (flags & FR_TRANSPARENT) {
 		GfxFillRect(left, top, right, bottom, PALETTE_TO_TRANSPARENT, FILLRECT_RECOLOUR);
@@ -423,7 +423,7 @@ static inline void DrawMatrix(const Rect
 		row_height = r.Height() / num_rows;
 	}
 
-	int col = GetColourGradient(colour, SHADE_6);
+	int col = GetColourGradient(colour, SHADE_LIGHTER);
 
 	int x = r.left;
 	for (int ctr = num_columns; ctr > 1; ctr--) {
@@ -437,7 +437,7 @@ static inline void DrawMatrix(const Rect
 		GfxFillRect(r.left + WidgetDimensions::scaled.bevel.left, x, r.right - WidgetDimensions::scaled.bevel.right, x + WidgetDimensions::scaled.bevel.top - 1, col);
 	}
 
-	col = GetColourGradient(colour, SHADE_4);
+	col = GetColourGradient(colour, SHADE_NORMAL);
 
 	x = r.left - 1;
 	for (int ctr = num_columns; ctr > 1; ctr--) {
@@ -469,8 +469,8 @@ static inline void DrawVerticalScrollbar
 	DrawImageButtons(r.WithHeight(height, false),  NWID_VSCROLLBAR, colour, up_clicked,   SPR_ARROW_UP,   SA_CENTER);
 	DrawImageButtons(r.WithHeight(height, true),   NWID_VSCROLLBAR, colour, down_clicked, SPR_ARROW_DOWN, SA_CENTER);
 
-	int c1 = GetColourGradient(colour, SHADE_3);
-	int c2 = GetColourGradient(colour, SHADE_7);
+	int c1 = GetColourGradient(colour, SHADE_DARK);
+	int c2 = GetColourGradient(colour, SHADE_LIGHTEST);
 
 	/* draw "shaded" background */
 	GfxFillRect(r.left, r.top + height, r.right, r.bottom - height, c2);
@@ -508,8 +508,8 @@ static inline void DrawHorizontalScrollb
 	DrawImageButtons(r.WithWidth(width, false), NWID_HSCROLLBAR, colour, left_clicked,  SPR_ARROW_LEFT,  SA_CENTER);
 	DrawImageButtons(r.WithWidth(width, true),  NWID_HSCROLLBAR, colour, right_clicked, SPR_ARROW_RIGHT, SA_CENTER);
 
-	int c1 = GetColourGradient(colour, SHADE_3);
-	int c2 = GetColourGradient(colour, SHADE_7);
+	int c1 = GetColourGradient(colour, SHADE_DARK);
+	int c2 = GetColourGradient(colour, SHADE_LIGHTEST);
 
 	/* draw "shaded" background */
 	GfxFillRect(r.left + width, r.top, r.right - width, r.bottom, c2);
@@ -547,8 +547,8 @@ static inline void DrawFrame(const Rect 
 
 	if (str != STR_NULL) x2 = DrawString(r.left + WidgetDimensions::scaled.frametext.left, r.right - WidgetDimensions::scaled.frametext.right, r.top, str, text_colour, align, false, fs);
 
-	int c1 = GetColourGradient(colour, SHADE_3);
-	int c2 = GetColourGradient(colour, SHADE_7);
+	int c1 = GetColourGradient(colour, SHADE_DARK);
+	int c2 = GetColourGradient(colour, SHADE_LIGHTEST);
 
 	/* If the frame has text, adjust the top bar to fit half-way through */
 	Rect inner = r.Shrink(ScaleGUITrad(1));
@@ -645,7 +645,7 @@ static inline void DrawResizeBox(const R
 	if (bevel) {
 		DrawFrameRect(r.left, r.top, r.right, r.bottom, colour, (clicked) ? FR_LOWERED : FR_NONE);
 	} else if (clicked) {
-		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(colour, SHADE_6));
+		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(colour, SHADE_LIGHTER));
 	}
 	DrawSpriteIgnorePadding(at_left ? SPR_WINDOW_RESIZE_LEFT : SPR_WINDOW_RESIZE_RIGHT, PAL_NONE, r.Shrink(ScaleGUITrad(2)), at_left ? (SA_LEFT | SA_BOTTOM | SA_FORCE) : (SA_RIGHT | SA_BOTTOM | SA_FORCE));
 }
@@ -685,7 +685,7 @@ void DrawCaption(const Rect &r, Colours 
 	DrawFrameRect(ir, colour, company_owned ? FR_LOWERED | FR_DARKENED | FR_BORDERONLY : FR_LOWERED | FR_DARKENED);
 
 	if (company_owned) {
-		GfxFillRect(ir.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(_company_colours[owner], SHADE_4));
+		GfxFillRect(ir.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(_company_colours[owner], SHADE_NORMAL));
 	}
 
 	if (str != STR_NULL) {
@@ -1906,7 +1906,7 @@ NWidgetCore *NWidgetMatrix::GetWidgetFro
 /* virtual */ void NWidgetMatrix::Draw(const Window *w)
 {
 	/* Fill the background. */
-	GfxFillRect(this->GetCurrentRect(), GetColourGradient(this->colour, SHADE_5));
+	GfxFillRect(this->GetCurrentRect(), GetColourGradient(this->colour, SHADE_LIGHT));
 
 	/* Set up a clipping area for the previews. */
 	bool rtl = _current_text_dir == TD_RTL;
@@ -2171,7 +2171,7 @@ void NWidgetBackground::Draw(const Windo
 	if (this->child != nullptr) this->child->Draw(w);
 
 	if (this->IsDisabled()) {
-		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_2), FILLRECT_CHECKER);
+		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_DARKER), FILLRECT_CHECKER);
 	}
 
 	DrawOutline(w, this);
@@ -2416,7 +2416,7 @@ void NWidgetScrollbar::Draw(const Window
 	}
 
 	if (this->IsDisabled()) {
-		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_2), FILLRECT_CHECKER);
+		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_DARKER), FILLRECT_CHECKER);
 	}
 
 	DrawOutline(w, this);
@@ -2867,7 +2867,7 @@ void NWidgetLeaf::Draw(const Window *w)
 	if (this->index >= 0) w->DrawWidget(r, this->index);
 
 	if (this->IsDisabled()) {
-		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_2), FILLRECT_CHECKER);
+		GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_DARKER), FILLRECT_CHECKER);
 	}
 
 	DrawOutline(w, this);