Hi Sepideh ,
As far as I know HighChart is a paid widget. That's why you may not find much information about it. If you do not particularly need it, I recommend you to use the basic charts of the mendix. I'm leaving a link about it below. I hope it works for you
https://docs.mendix.com/refguide/charts-configuration/
Regards
Ridvan
You actually can display different colors on a bar chart if you make multiple series. If you make a microflow to sort out each category, then set the microflows as the data source, you can set the color for each series.