What secret things are happening to my NSButtonCell?

Question

I'm writing an OS X app (target 10.10, Xcode 6.1) and I'm really confused by my custom NSButtonCell subclass. It seems like there are things going on here that shouldn't. I'm new to OS X programming, so I'm asking if anyone has insight into the inner workings of NSButtonCell.

First, what seems to be working?

1. I can set the button's image and title. The image appears normally.
2. The storyboard sets up the button to be Style: Textured and Type: Momentary Change. It's not Bordered, not Transparent, and doesn't allow Mixed State.

List of complaints:

1. I override -drawTitle:withFrame:inView: to draw the title in a custom color depending on the cell's highlighted. This color should be #cccccc when the cell is not highlighted, but it's actually #d6d6d6.
2. The button has both image and alternate image. The image that's drawn is never the alternate image, so I override -drawImage:withFrame:inView: to pick the correct image for cell's highlighted. This appears to work, but what the heck, NSButtonCell? How is on/off state different from highlighted? I've tried many of the Type options and none seem to change the fact that pressing the button will momentarily change highlighted, and toggle state.
3. Speaking of momentarily changing highlighted, it appears that its duration is about as short as possible, so I had to implement a sort of "debouncer" to prevent -drawWithFrame:inView: from being called more frequently than a specified threshold.
4. My button cell also has properties myBackgroundColor and myAlternateBackgroundColor. I'm not using backgroundColor because I need to be able to draw a custom background shape (filled rect, filled circle, etc). The alternate background color is used when highlighted. The problem here is that the alternate background color should be #93edbf but appears to be #a1eecb! In order to get it to look like #93edbf, I need to set the color to #84ecb2.
5. So far this has all been about one particular instance of this button cell. But in another instance, the alternate background isn't drawing at all! I've read through the storyboard code and the buttons are as identical as they can be. My view controller code likewise updates both button cells' properties at the same time. Why would one button behave differently from another?
6. I want the button to highlight on mouse down instead of "momentarily" after mouse up. I haven't yet implemented this in my custom cell. Man, NSButtonCell is really lacking some things. How does something like that happen? Don't the OS X and iOS teams ever talk to each other?

What could it be?

I've already verified that the cell's controlTint is set to NSClearControlTint. I've checked for background filters, compositing filters and content filters on the off chance they had anything to do with this.

I know Apple really wants us to use their native look and feel for UI elements, but I never thought they'd go so far as to force the use of some highlight tint.