There is currently no hexadecimal mask for the MaskEdit cell. I will forward your request to the tools team to see what would have to be done to add support for such a mask.
You could also handle this yourself in a straight-forward manner using a grid event like CurrentCellValidateString.
private void gridControl1_CurrentCellValidateString(object sender, GridCurrentCellValidateStringEventArgs e)
{
//identify the cell somehow - we assume col2 is the hex col
GridCurrentCell cc = this.gridControl1.CurrentCell;
if(cc.ColIndex == 2)
{
foreach (char c in e.Text)
{
char c1 = c.ToString().ToLower()[0];
if("abcdef0123456789".IndexOf(c1) == -1)
{
e.Cancel = true;
break;
}
}
}
}