title: ngx-charts colors does not show correctly Angular 6?
body: <p>I am trying to add color to the stacked bar graph using ngx-charts in angular 6. I use the array to add colors, But at each time color changes automatically. Whenever I request data color changes automatically. Is there any function or technique to assign colors to ngx-charts to each data manually in angular 6? 
  Here is my HTML code</p>
  
  <pre><code>&lt;ngx-charts-bar-vertical-stacked [scheme]="colorScheme"
                          [results]="multi" [gradient]="gradient" [xAxis]="showXAxis"
                          [yAxis]="showYAxis" [legend]="showLegend"
                          [showXAxisLabel]="showXAxisLabel"
                          [showYAxisLabel]="showYAxisLabel" [xAxisLabel]="xAxisLabel"
                          [yAxisLabel]="yAxisLabel" [view]="  " (select)="onSelect($event)"&gt;
  </code></pre>
  
  <p>
  Here is the array of colors I used in my typescript file</p>
  
  <pre><code>colorScheme = { 
  domain: ['red', 'green','blue','pink','black']  };
  </code></pre>