Changing the color of NSProgressIndicator?

You can use Quartz filters (e.g. hue adjust) for this directly in Interface Builder. This works better than expected.

It's in the Effects Inspector. Under "Content Filters" you can add "Hue Adjust"

Use "CIFalseColor" filter to get white color and more.

let colorFilter = CIFilter(name: "CIFalseColor")!
colorFilter.setDefaults()
colorFilter.setValue(color1, forKey: "inputColor0")
colorFilter.setValue(color2, forKey: "inputColor1")
proggressBar?.contentFilters = [colorFilter]