How to change the BackColor of a single cell
The style object holds all the information that affects the cells appearance. One property contained in the style object is its BackColor. Use a two-parameter indexer (rowIndex, colIndex) on your GridControl object to get a reference to that particular cells style, a GridStyleInfo object.
//Changes the BackColor of a cell in the 1st row and 3rd column. gridControl1[1, 3].BackColor = Color.Red;
'Changes the BackColor of a cell in the 1st row and 3rd column. GridControl1(1, 3).BackColor = Color.Red