Hi,

You can use this free app from the store for the same:  https://apps.odoo.com/apps/modules/16.0/kg_required_fields/

Thanks

I use this module for 16 or 17

https://apps.odoo.com/apps/modules/17.0/mandatory_field_highlight

Hi, 

You can achieve this by adding a css file and inside give 

.o_required_modifier.o_field_widget {
background-color: rgb(226 222 147) !important;
} 

This gives a slight yellow color to all the required fields. Add the css file in web.assets_backend.

Regards