You can change the default chart styles for all the Application Insights charts. By default, you will find them in the line chart but depends on your need you can change the representation to Area, bar or grid chart. You can also customize the chart colors and grouping of data representations.
Change Application Insights Chart Styles
To change the style of any of Application Insight chart, click on the edit button associated with Chart.
This will bring the “Chart details” blade, from where you can customize the chart.
Choose the Chart type for specific types of charts and also change the color palette for the different color mode.