File variables.scss not working when i run code in android device

hello everyone
i have a problem with variables when i build and run app in my device android

this code work when i use ‘ionic serve’ in browser and the ion-content background take this color
(–ion-color-primary: #3880ff)
but when i run this code in android this color not work and ion-content stay transparent also
ion-botton not get primary color by default is also stay without color

example code
when i use ionic serve

and when i use ionic cordova run android

ionic -v : 5.2.1
cordova -v : 9.0.0 (cordova-lib@9.0.1)
Angular CLI: 7.3.9
Node: 10.16.0
OS: win32 x64
Angular: 7.2.15

I tried exactly what you did and it shows up perfectly find for me, on my Motorola Moto G5 plus Android device.

My specs:

  $ ionic info


   Ionic CLI                     : 5.2.1 (/usr/local/lib/node_modules/ionic)
   Ionic Framework               : @ionic/angular 4.6.1
   @angular-devkit/build-angular : 0.13.9
   @angular-devkit/schematics    : 7.3.9
   @angular/cli                  : 7.3.9
   @ionic/angular-toolkit        : 1.5.1


   Cordova CLI       : 9.0.0
   Cordova Platforms : android 8.0.0
   Cordova Plugins   : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 4.1.1, (and 4 other plugins)


   cordova-res : 0.5.1 (update available: 0.6.0)
   native-run  : 0.2.7


   Android SDK Tools : 26.1.1 (/Users/vtn2/Library/Android/sdk)
   ios-deploy        : 1.9.4
   NodeJS            : v10.14.2 (/usr/local/bin/node)
   npm               : 6.9.0
   OS                : macOS Mojave
   Xcode             : Xcode 10.2.1 Build version 10E1001

And, I learned about ionic cordova run android, which I’ve never seen before. Very convenient!