Hello Rishi,
You can certainly achieve this via custom code.
However, it is not required because you can change the Legend font style from the Designer >> Values Grouping Editor >> Legend >> Text Style
If you would like to change the size of the Legend items (markers), you can do that from the Designer >> Chart >> Legends >> General tab (Marks Width and Height).
Hopefully this helps.
Best Regards,
Nevron Support Team