message: Added a background linear gradient to color control parameters
diff: @@ -248,7 +248,10 @@ export class ColorControl extends SimpleParam<PD.Color> {
  }
  renderControl() {
  - return <select value={this.props.value} onChange={this.onChange} style={{ borderLeft: `16px solid ${Color.toStyle(this.props.value)}` }}>
  + let rgb: any[] = Color.toStyle(this.props.value).replace('rgb(', '').split(', ');
  + rgb = rgb.map(c => parseInt(c));
  + let secondArg = `rgb(${rgb[0]}, ${rgb[1]}, ${rgb[2]}, 0.0)`;
  + return <select value={this.props.value} onChange={this.onChange} style={{background: `linear-gradient(90deg, ${Color.toStyle(this.props.value)}, ${secondArg})`}}>
  {ColorValueOption(this.props.value)}
  {ColorOptions()}
  </select>;
  