If we did have a black PM, the howler-monkey noise from the Left would be overwhelming. 'Ooo, victory against racism and a blow for tolerance', etc. As in the US with Carter, a party could play the race card whenever criticism of the leadership gets too hot. But what of the policies?
When Margaret Thatcher came to power, people we now call PC choked on their breakfast lentils. She wasn't supposed to be a Tory! All that shouting and pushing people about in the name of womens' rights wasted! The first woman PM was supposed to be one of THEM, crusading against the evil forces of chauvanist maledom. I heard that argument a few times.
I look forward to the first black PM, not that we need one for colour, being a Tory. A sound one as well (not one like Sayeeda Warsi who puts herself out as heavy and morally conservative to her fellow Muslims but all trendy and progressive to the rest of us). He/she could go to the Proms and please Margaret Hodge. And it would really annoy the likes of Peter Tatchell to have a God-fearing, morally upright black person in charge, incensed as he is already at the 'racist' rules of Royal lineage not being able to give us a black monarch any time soon!
(And anyway, perhaps the question should be Should We Have A Black European Union President?! There are too many white people up there too you know!)