Looking at recent exit polls:
2018 House Election:
86% of Republican voters were white
7% Hispanic of any race
3% other
2% black
1.5% Asian
2016 Presidential Election:
86% white
7% Hispanic of any race
2.5% Asian
2.5% other
2% black
Completely unsurprisingly, the states that "look" more like the Republican Party, or at least Republican voters, seem to be Utah, Idaho, Wyoming and Nebraska.
Of course as Patrick97 suggested many people who vote Republican are not actually registered Republicans.
While I suspect "registered Republicans" (or, more usefully, people who regularly vote in GOP primaries and caucuses, as some states don't have partisan registration) are slightly more White than GOP electoral coalitions, I am not 100% sure. For all of these minorities who might not consider themselves Republicans but voted GOP in 2016 or 2018, surely there are a decent number of minorities who DO usually consider themselves Republicans and voted for Clinton in 2016 or Democratic in 2018, too.
Probably there are a lot more of the latter given how Vietnamese, Cuban, etc. immigrants swung in 2016.
