We had the same situation a few years ago in the Alexandria National Cemetery in Pineville, La. I was walking through there one day and found several graves of soldiers of the US Colored Troops buried under Confederate markers. I figured there had to be a very interesting story behind that, but when I talked to cemetery officials, I found that the colored soldiers had some old chipped up markers, so they'd been replaced - with the pointed Confederate stones, but the correct USCT unit designations. Once the error - and obvious insult to everyone involved, of both Southern and Northern sympathies - was pointed out, the stones were replaced again, this time with correct round-top markers. Everyone is happy now.