Younger Americans are more diverse than older Americans, certainly, and more likely to hold liberal political views. (They are also less likely to be members of political parties.) One effect of this is that the Republican Party skews older than the Democratic Party and, therefore, that boomers make up more of the GOP than the Dems though the generation itself is fairly evenly divided.
What did the overlap of White Americans, Republicans and baby boomers look like? So, using data from the 2020 edition of the American National Election Studies, Gallup and the Census Bureau, I was able to create this Venn diagram.
What I love about this diagram (seen on p. 126, if you have a copy of the book) is that it represents a lot of information very simply. It is admittedly hard to parse percentages or segments from overlapping circles, but you clearly get a sense that a lot of boomers are White Republicans (4 in 10) and that the GOP is heavily White. A quarter of the party is White baby boomers, per this analysis.