dynamic

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  classNames: 'my-component',

  didReceiveAttrs() {
    this._updateVariables();
  },
  
  didInsertElement() {
    this._updateVariables();
  },
  
  _updateVariables() {
    let style = this.get('element.style');
    if (style) {
      style.setProperty('--foreground-color', this.get('foreground'));
      style.setProperty('--gradient-color-dark', this.get('dark'));
      style.setProperty('--gradient-color-light', this.get('light'));
    }
  }
});

styles.app.css

.my-component {
  margin: 1em;
  padding: 1em;
  background: lightblue;
}

.my-component .child-element {
    color: var(--foreground-color);
  background:
    var(--gradient-color-dark)
    linear-gradient(var(--gradient-color-dark), var(--gradient-color-light));
}

templates.application.hbs

{{#my-component dark='#090' light='#6f6'}}
  green
{{/my-component}}

{{#my-component dark='#333' light='#888' foreground='white'}}
  hello
{{/my-component}}

templates.components.my-component.hbs

<div class="child-element">
	.child-element
</div>

{{yield}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}