Shimmer or Twinkle effect

I am trying to put together a 50's themed module, so naturally I have some stars on the title page, along with some others. Is there any way to have them twinkle a little, maybe change colors, so they look period authentic? 

Here's the one catch... they have to loop as well. Basically the stars will twinkle as long as the slide is shown...

Here is a pic of my title screen for reference.

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