Angular 4 (click) changes the class of element on another component

I have one root component. One root component has 3 child component:

In PressComponent I have a button with (click)="changeColors())".

In CalcComponent I have a box with blue background.

In PianoComponent I have a box with red background.


How can I do this:

When I click on button in PressComponent then:

In CalcComponent box will get the class .calc-box-green.

In PianoComponent box will get the class .piano-box-yellow.

Plunker example

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