How do I set UITableViewCellSelectionStyle property to some custom color?

The best way to set the selection is to set the selectedBackgroundView on the cell when you construct it.

i.e.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
        cell.selectedBackgroundView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"SelectedCellBackground.png"]] autorelease];
    }

    // configure the cell
}

The image used should have a nice gradient (like the default selection). If you just want a flat color, you can use a UIView instead of a UIImageView and set the backgroundColor to the color you want.

This background is then automatically applied when the row is selected.