Tested in Mendix 7.8.
The current date has a dijitCalendarCurrentDate class on the td. You can style this with custom css.
For example: you can give it the same style as the selected date.
border-radius: 50%;
background: #0595DB;
There is a widget in the appstore that might provide what you want: https://appstore.home.mendix.com/link/app/1799/FlowFabric-BV/Bootstrap-Datepicker
Regards,
Ronald