What you see is a huge difference, within the GOP, between those appointed and those elected. In recent times, there have been quite a few really major appointees among Republicans -- Clarence Thomas, Condaleeza Rice, Colin Powell, Michael Steele, etc. But those don't indicate a willingness by Republican voters, generally, to support black people. Instead they indicate a willingness by the Republican elite to do so (or, more cynically, you could say they indicate a recognition by the Republican elite that they need some token diverse appointees to combat the appearance of racism).
This was really driven home a few years back (maybe 2008) at the Republican convention. Up on stage, there were a huge number of black people that year. Yet, when the camera swung around to show the crowd, it was a sea composed of almost entirely pale faces. And those blacks who did make it up on stage were nearly always appointees instead of elected officials.
I invite you to try something out. Name a black Republican who has won a state-wide election against a white opponent in the last thirty years. Just one. It can be a governorship or a Senate position, or a state-level vote for the presidency, or a primary for one of those three.
Every four years there are fifty primaries/caucuses and 50 general elections, just for the presidency, as well as 50 gubernatorial races, and there are 100 Senate races every six years. Counting primaries and generals, that's around 3000 separate state-wide races since 1980. How many of those 3000 have black Republicans won?
One or two, maybe? How many against white opponents, where the racist voters in the Republican base actually had an option to vote racial identity? Any? On the Democratic side, Jesse Jackson won more state-wide elections in a single primary season than all the black Republican candidates in all the state-wide elections in all the years since then, and Jackson wasn't even particularly successful (much less so than Obama, for example). Democrats certainly show a profound preference for white candidates, but not to the near-total exclusion of all others, the way Republicans do.