WatchOS: Modular small complication issue. Apple's Calculator and Activity complication have 3 colors. How?

The title says it all. How to display a 3 color image in a modular small complication? All the modular small complication template take a CLKImageProvider which can at most have 2 colors. And yet, Apple's calculator and activity complications have 3 colors in addition to a clear background. How is that done?

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WatchOS: Modular small complication issue. Apple's Calculator and Activity complication have 3 colors. How?
 
 
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