Define borderRadius, change colors to consts

index.js

-const red = "#c50505";
-const blue = "#0479a8";
+const colorRed = "#c50505";
+const colorBlue = "#0479a8";
+const colorBlackFont = "#282728";
+const colorGrayLight = "#adadad";
 
 export const theme = {
   props: {
@@ -14,21 +16,21 @@ export const theme = {
     MuiOutlinedInput: {
       root: {
         "&:hover $notchedOutline": {
-          borderColor: blue,
+          borderColor: colorBlue,
         },
         "@media (hover: none)": {
           "&:hover $notchedOutline": {
-            blue,
+            blue: colorBlue,
           },
         },
         "&$focused $notchedOutline": {
-          borderColor: blue,
+          borderColor: colorBlue,
         },
       },
     },
     MuiListSubheader: {
       root: {
-        color: "#adadad",
+        color: colorGrayLight,
         fontWeight: "bolder",
       },
     },
@@ -36,13 +38,16 @@ export const theme = {
   palette: {
     type: "light",
     primary: {
-      main: red,
+      main: colorRed,
     },
     secondary: {
-      main: blue,
+      main: colorBlue,
     },
     text: {
-      primary: "#282728",
+      primary: colorBlackFont,
     },
   },
+  shape: {
+    borderRadius: 2,
+  },
 };