There's a couple of approaches:
1) Color Correction > Color Reduce
2) Color Correction > Gradient Colorize
Either one of those
+ Stylize > MinMax (either mode) and possibly some blur (your choice)
Under the Motion menu > Provide Motion Feedback and request to get those filters back. There were also a ton of (Library > ) Filter and Generator Image Units that were removed too. They didn't *all* work in Motion, but a good many of them did.