add themePreviewColor to theme

src/theme/DarkTheme.ts

@@ -13,6 +13,7 @@ const colorSpecial = "#337a44";
 const darkTheme: Theme = {
   id: "2",
   name: "Dark Theme",
+  themePreviewColor: colors.primary,
   background: colors.primary,
   appBarBgColor: colors.secondary,
   textColor: colors.primary,

src/theme/GreyTheme.ts

@@ -3,6 +3,7 @@ import { Theme } from "./Theme";
 const greyTheme: Theme = {
   id: "1",
   name: "Grey Theme",
+  themePreviewColor: "#4D606E",
   background: "#EEEEEE",
   appBarBgColor: "#e4e4e4",
   textColor: "#4D606E",

src/theme/LightTheme.ts

@@ -5,6 +5,7 @@ const colorSpecial = "#8B8B8B";
 const lightTheme: Theme = {
   id: "1",
   name: "Light Theme",
+  themePreviewColor: "#9B9B9B",
   background: "#BBBBBB",
   appBarBgColor: "#7B7B7B",
   textColor: "#5B5B5B",

src/theme/Theme.ts

@@ -1,6 +1,7 @@
 export type Theme = {
   id: string;
   name: string;
+  themePreviewColor: string; // for theme switch menu
   textColor: string;
   textLightColor: string;
   background: string;