Adding directive to app.module.ts

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { ColorDirective } from './color.directive'; //import the color directive

@NgModule({
  declarations: [
    AppComponent,
    ColorDirective //added here
  ],
  imports: [
    BrowserModule
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }