CSS

Vuetify v-data-table custom row hover background color (Light Theme)

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

Vuetify v-data-table custom row hover background color (Dark Theme)

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