gray背景改名fixColor，允许自定义颜色

parts/scenes/app_dtw.lua

@@ -199,7 +199,8 @@ local scene={}
 
 function scene.sceneInit()
     reset()
-    BG.set('gray')
+    BG.set('fixColor')
+    BG.send(.26,.26,.26)
     BGM.play(bgm)
 end
 

parts/scenes/app_mahjong.lua

@@ -86,6 +86,8 @@ end
 local scene={}
 
 function scene.sceneInit()
+    BG.set('fixColor')
+    BG.send(.26,.62,.26)
     _newGame()
     selected=false
 end

parts/scenes/app_tap.lua

@@ -12,7 +12,8 @@ function scene.sceneInit()
     lastKey=nil
     speed=0
     keyTime={}for i=1,40 do keyTime[i]=-1e99 end
-    BG.set('gray')
+    BG.set('fixColor')
+    BG.send(.26,.26,.26)
     BGM.play('push')
 end