diff --git a/frontend/apps/reader/modules/readercropping.lua b/frontend/apps/reader/modules/readercropping.lua
index c5a75b490..9e44df430 100644
--- a/frontend/apps/reader/modules/readercropping.lua
+++ b/frontend/apps/reader/modules/readercropping.lua
@@ -93,7 +93,7 @@ function ReaderCropping:onPageCrop(mode)
     self.orig_view_dimen = Geom:new{w = self.view.dimen.w, h = self.view.dimen.h}
     -- backup original view bgcolor
     self.orig_view_bgcolor = self.view.outer_page_color
-    self.view.outer_page_color = Blitbuffer.gray(0.5) -- gray bgcolor
+    self.view.outer_page_color = Blitbuffer.COLOR_GREY
     -- backup original page scroll
     self.orig_page_scroll = self.view.page_scroll
     self.view.page_scroll = false
diff --git a/frontend/apps/reader/modules/readerview.lua b/frontend/apps/reader/modules/readerview.lua
index bd8c36927..b6e793699 100644
--- a/frontend/apps/reader/modules/readerview.lua
+++ b/frontend/apps/reader/modules/readerview.lua
@@ -43,7 +43,7 @@ local ReaderView = OverlapGroup:new{
     page_gap = {
         width = Screen:scaleBySize(8),
         height = Screen:scaleBySize(8),
-        color = Blitbuffer.gray(0.5),
+        color = Blitbuffer.COLOR_GREY,
     },
     -- DjVu page rendering mode (used in djvu.c:drawPage())
     render_mode = DRENDER_MODE, -- default to COLOR
diff --git a/frontend/ui/widget/button.lua b/frontend/ui/widget/button.lua
index 9c106b8f7..1977c31f0 100644
--- a/frontend/ui/widget/button.lua
+++ b/frontend/ui/widget/button.lua
@@ -35,7 +35,7 @@ function Button:init()
     if self.text then
         self.label_widget = TextWidget:new{
             text = self.text,
-            fgcolor = Blitbuffer.gray(self.enabled and 1.0 or 0.5),
+            fgcolor = self.enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_GREY,
             bold = self.text_font_bold,
             face = Font:getFace(self.text_font_face, self.text_font_size)
         }
@@ -114,7 +114,11 @@ end
 function Button:enable()
     self.enabled = true
     if self.text then
-        self.label_widget.fgcolor = Blitbuffer.gray(self.enabled and 1.0 or 0.5)
+        if self.enabled then
+            self.label_widget.fgcolor = Blitbuffer.COLOR_BLACK
+        else
+            self.label_widget.fgcolor = Blitbuffer.COLOR_GREY
+        end
     else
         self.label_widget.dim = not self.enabled
     end
@@ -123,7 +127,11 @@ end
 function Button:disable()
     self.enabled = false
     if self.text then
-        self.label_widget.fgcolor = Blitbuffer.gray(self.enabled and 1.0 or 0.5)
+        if self.enabled then
+            self.label_widget.fgcolor = Blitbuffer.COLOR_BLACK
+        else
+            self.label_widget.fgcolor = Blitbuffer.COLOR_GREY
+        end
     else
         self.label_widget.dim = not self.enabled
     end
diff --git a/frontend/ui/widget/buttontable.lua b/frontend/ui/widget/buttontable.lua
index b3002dd6d..5ec6c453e 100644
--- a/frontend/ui/widget/buttontable.lua
+++ b/frontend/ui/widget/buttontable.lua
@@ -55,7 +55,7 @@ function ButtonTable:init()
             }
             local button_dim = button:getSize()
             local vertical_sep = LineWidget:new{
-                background = Blitbuffer.gray(0.5),
+                background = Blitbuffer.COLOR_GREY,
                 dimen = Geom:new{
                     w = self.sep_width,
                     h = button_dim.h,
@@ -85,7 +85,7 @@ function ButtonTable:addHorizontalSep()
     table.insert(self.container,
                  VerticalSpan:new{ width = Screen:scaleBySize(2) })
     table.insert(self.container, LineWidget:new{
-        background = Blitbuffer.gray(0.5),
+        background = Blitbuffer.COLOR_GREY,
         dimen = Geom:new{
             w = self.width,
             h = self.sep_width,
diff --git a/frontend/ui/widget/dictquicklookup.lua b/frontend/ui/widget/dictquicklookup.lua
index d27aa6438..5088a9879 100644
--- a/frontend/ui/widget/dictquicklookup.lua
+++ b/frontend/ui/widget/dictquicklookup.lua
@@ -212,7 +212,6 @@ function DictQuickLookup:update()
         show_parent = self,
     }
     local title_bar = LineWidget:new{
-        --background = Blitbuffer.gray(0.5),
         dimen = Geom:new{
             w = button_table:getSize().w + self.button_padding,
             h = Screen:scaleBySize(2),
diff --git a/frontend/ui/widget/inputtext.lua b/frontend/ui/widget/inputtext.lua
index d4755382c..2de3bd35d 100644
--- a/frontend/ui/widget/inputtext.lua
+++ b/frontend/ui/widget/inputtext.lua
@@ -113,7 +113,7 @@ function InputText:initTextBox(text)
         bordersize = self.bordersize,
         padding = self.padding,
         margin = self.margin,
-        color = Blitbuffer.gray(self.focused and 1.0 or 0.5),
+        color = self.focused and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_GREY,
         self.text_widget,
     }
     self.dimen = self[1]:getSize()
@@ -138,7 +138,7 @@ end
 function InputText:unfocus()
     self.focused = false
     self.text_widget:unfocus()
-    self[1].color = Blitbuffer.gray(0.5)
+    self[1].color = Blitbuffer.COLOR_GREY
 end
 
 function InputText:focus()
diff --git a/frontend/ui/widget/linkbox.lua b/frontend/ui/widget/linkbox.lua
index 1b4c6829e..3dec77834 100644
--- a/frontend/ui/widget/linkbox.lua
+++ b/frontend/ui/widget/linkbox.lua
@@ -8,7 +8,7 @@ local Blitbuffer = require("ffi/blitbuffer")
 
 local LinkBox = InputContainer:new{
     box = nil,
-    color = Blitbuffer.gray(0.5),
+    color = Blitbuffer.COLOR_GREY,
     radius = 0,
     bordersize = 2,
 }
diff --git a/frontend/ui/widget/toggleswitch.lua b/frontend/ui/widget/toggleswitch.lua
index 79419f20d..bce536629 100644
--- a/frontend/ui/widget/toggleswitch.lua
+++ b/frontend/ui/widget/toggleswitch.lua
@@ -28,7 +28,7 @@ local ToggleSwitch = InputContainer:new{
     width = Screen:scaleBySize(216),
     height = Screen:scaleBySize(30),
     bgcolor = Blitbuffer.COLOR_WHITE, -- unfoused item color
-    fgcolor = Blitbuffer.gray(0.5), -- focused item color
+    fgcolor = Blitbuffer.COLOR_GREY, -- focused item color
     font_face = "cfont",
     font_size = 16,
     enabled = true,
@@ -42,7 +42,7 @@ function ToggleSwitch:init()
 
     self.toggle_frame = FrameContainer:new{
         background = Blitbuffer.COLOR_WHITE,
-        color = Blitbuffer.gray(0.5),
+        color = Blitbuffer.COLOR_GREY,
         radius = 7,
         bordersize = 1,
         padding = 2,
@@ -70,7 +70,7 @@ function ToggleSwitch:init()
         }
         local button = FrameContainer:new{
             background = Blitbuffer.COLOR_WHITE,
-            color = Blitbuffer.gray(0.5),
+            color = Blitbuffer.COLOR_GREY,
             margin = 0,
             radius = 5,
             bordersize = 1,
diff --git a/frontend/ui/widget/touchmenu.lua b/frontend/ui/widget/touchmenu.lua
index 88ca06b0f..a3fd72f19 100644
--- a/frontend/ui/widget/touchmenu.lua
+++ b/frontend/ui/widget/touchmenu.lua
@@ -79,7 +79,7 @@ function TouchMenuItem:init()
             },
             TextWidget:new{
                 text = self.item.text or self.item.text_func(),
-                fgcolor = Blitbuffer.gray(item_enabled ~= false and 1.0 or 0.5),
+                fgcolor = item_enabled ~= false and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_GREY,
                 face = self.face,
             },
         },