[Vuejs]-Conditional css on hover based on class of row of Vuetify simple table

Try with the !important property to ensure you override any conflicting vuetify CSS

tr.greenBG:hover { 
  background-color: green !important
} 

if you really want to avoid using !important you need to be as specific as vuetify’s CSS selector:

.v-data-table__wrapper
  table
  tbody
  tr.greenBG:hover:not(.v-data-table__expanded__content):not(.v-data-table__empty-wrapper) {
  background: green;
}