If that happened , and then no candidate for vice president got 270 electoral votes , then the US Senate would pick the vice president.
If the 30 electors voted for a Democrat vice president, conceivably you could have a Democrat vice president along with the Republican president in such a scenario.
In the original text of the Constitution, the presidential candidate with the second-most votes would become Vice President, so in practice the two would virtually always be of separate parties.
It only took four election cycles to determine that this system was untenable (imagine if Donald Trump was Joe Biden’s VP) so in 1804 the 12th Amendment was ratified, which changed it so that the president and VP are elected on separate ballots. However in the mid-19th century it became the norm for a presidential and vice presidential candidate to run together as “running mates” so in practice they would always both receive the same number of votes. Additionally, although the electoral college technically selects them separately, on the actual state ballots voters only cast one vote for a presidential-VP pair (I can’t determine if there are any states that don’t do it this way).
So strictly speaking it is possible for the president and VP to be of different parties, but only if the president picks someone of the other party to be their running mate. This has happened; Republican Abraham Lincoln picked Democrat Andrew Johnson as his running mate in a bid to foster national unity, although the fact that Johnson became president after Lincoln was murdered pretty much put an end to the practice, and no successful presidential candidate has chosen a running mate of the opposite party since. Republican John McCain reportedly considered Democrat Joe Lieberman to be his running mate in 2008, but he ultimately chose Sarah Palin and the rest is history.
https://www.reddit.com/r/AskAnAmerican/comments/o72p5m/can_a_president_and_a_vice_president_be_from/