You can display the Extended Hours data on intraday charts either by choosing the option Extended in the bottom right corner or in the Symbol tab in the chart settings. There you can also change or remove the tint that highlights Extended Hours data on the chart by default.
Please note that not all exchanges have Extended Hours data. If no Extended Hours data for the symbol is available, the Ext button will not be shown in the bottom right corner of the chart.
However, the Extended Hours option in the Chart settings will still be present, but it will not change anything if the Extended Hours data for that symbol is not available.