Highlight object groups in keynote I have 3 groups on a slide that I want to highlight 1 at a time.  Is there a good way to do this?  My slide has a gradient background so putting a rectangle over the objects and faking it mucking with their transparency doesn't seem like a good approach.

Is there a way to make objects start out opacified?  If so, I can use the opacity action on the objects, but when I tried to use an opacity action, on transition, with duration 0, it didn't work.  Having a short (0.1s) duration causes kind of a jarring flicker.

I also thought about using multiple slides with magic-move handling the opacity changes, but I didn't see a way to change the opacity of a group.  

I'm running Keynote 6.5.2 on Yosemite (the most recent releases of both I believe).
I've built a small demo Keynote file (v5.1, on Mac OS 10.6.8, hope you can open it) -- this does what you're trying to achieve. At start only group 1 is fully opaque, then after each click, group 2 and 3 gain full opacity while the other groups are 50% transparent.
I've solved the 0.1s flicker by putting a copy of the groups underneath group 2 and 3 and setting it to 0% transparency at the beginning.
It could use some tweaking, I'll admit that, but that was just a quick 2am demo.