Change NSTableView alternate row colors

Swift 4+ version of AlternateRealist's answer:

public class AlternateBgColorTableView: NSTableView {
    var alternateBackgroundColor: NSColor? = .red

    override public func drawBackground(inClipRect clipRect: NSRect) {
        // If we didn't set the alternate color, fall back to the default behavior
        guard let alternateBackgroundColor = alternateBackgroundColor else {
            super.drawBackground(inClipRect: clipRect)

            return
        }

        // Fill in the background color
        backgroundColor.set()
        clipRect.fill()

        // Check if we should be drawing alternating colored rows
        if usesAlternatingRowBackgroundColors {
            // Set the alternating background color
            alternateBackgroundColor.set()

            // Go through all of the intersected rows and draw their rects
            var checkRect = bounds
            checkRect.origin.y = clipRect.origin.y
            checkRect.size.height = clipRect.height
            let rowsToDraw = rows(in: checkRect)
            var currentRow = rowsToDraw.location

            repeat {
                if currentRow % 2 != 0 {
                    // This is an alternate row
                    var rowRect = rect(ofRow: currentRow)
                    rowRect.origin.x = clipRect.origin.x
                    rowRect.size.width = clipRect.width
                    rowRect.fill()
                }

                currentRow += 1
            } while currentRow < rowsToDraw.location + rowsToDraw.length

            // Figure out the height of "off the table" rows
            var thisRowHeight = rowHeight

            if gridStyleMask.contains(.solidHorizontalGridLineMask) || gridStyleMask.contains(.dashedHorizontalGridLineMask) {
                thisRowHeight += 2 // Compensate for a grid
            }

            // Draw fake rows below the table's last row
            var virtualRowOrigin: CGFloat = 0
            var virtualRowNumber = numberOfRows

            if numberOfRows > 0 {
                let finalRect = rect(ofRow: numberOfRows - 1)
                virtualRowOrigin = finalRect.origin.y + finalRect.height
            }

            repeat {
                if virtualRowNumber % 2 != 0 {
                    // This is an alternate row
                    let virtualRowRect = NSRect(x: clipRect.origin.x, y: virtualRowOrigin, width: clipRect.width, height: thisRowHeight)
                    virtualRowRect.fill()
                }

                virtualRowNumber += 1
                virtualRowOrigin += thisRowHeight
            } while virtualRowOrigin < clipRect.origin.y + clipRect.size.height

            // Draw fake rows above the table's first row
            virtualRowOrigin = -1 * thisRowHeight
            virtualRowNumber = -1

            repeat {
                if abs(virtualRowNumber) % 2 != 0 {
                    // This is an alternate row
                    let virtualRowRect = NSRect(x: clipRect.origin.x, y: virtualRowOrigin, width: clipRect.width, height: thisRowHeight)
                    virtualRowRect.fill()
                }

                virtualRowNumber -= 1
                virtualRowOrigin -= thisRowHeight
            } while virtualRowOrigin + thisRowHeight > clipRect.origin.y
        }
    }
}

If you wish to set a custom color paired with the data in each row, I found this way of doing so, thanks to the posts here above, and this solution is also working to implement a custom alternate row color ( except for the empty rows ) :

create a subclass of NSTableView :

ColoredRowTableView.h

   @protocol ColoredRowTableViewDelegate <NSTableViewDelegate>
   -(NSColor *)colorForRow:(NSInteger)row;
   @end
   @interface ColoredRowTableView : NSTableView
   @end

in ColoredRowTableView.m

- (void)drawRow:(NSInteger)row clipRect:(NSRect)clipRect
{
    if (row == [self selectedRow])
    {
        [super drawRow:row clipRect:clipRect];
         return;
    }
    NSColor *color = [(id<ColoredRowTableViewDelegate>)[self delegate] colorForRow:row];
    [color setFill];
    NSRectFill([self rectOfRow:row]);
    [super drawRow:row clipRect:clipRect];
}

then in your table view delegate :

#import "ColoredRowTableView.h"
@interface MyTableViewDelegate : NSViewController <ColoredRowTableViewDelegate>
// instead of <NSTableViewDelegate>

implement the colorForRow: method in your delegate. If the goal is only to provide alternate row it can return a color based on the row number, if it is even or odd. Also don't forget to change the class of your table view to ColoredRowTableView in interface builder