An anonymous tipster writes in: Perhaps there are some developers who need to change the backcolor of a single cell of a WGrid. I have solved this problem with the DrawItem event of the grid:

DrawItem event of the grid
{
    //this change the cell-backcolor
    if( (event->itemID == wanted_row) && (event->itemData == wanted_column) )
    {
        event->canvas->SetBrush( WColor( WColorGreen ) );
    }


    //this change the selection-color
    if( event->state == WDrawItemSelected )
    {
        event->state = (WDrawItemState) 0;
        event->canvas->SetBrush( WColor( WColorRed ) );
    }


    return FALSE;
}

If you want to change the color of a cell you have to call: grid->Update(TRUE);

Or for the version by Herbert Menke: WRect rect = grid->GetRectangle( row, col ); grid->Invalidate( rect, true );