You can assign a category name to each title color and use it as a category.
Go to Settings → Presets → “Category Names”
Organize reminders into categories by color
When creating a reminder for someone’s birthday,
select the same title color each time.
On the reminder list screen, tap Search.
In other words, you can organize and display reminders by category (group) using colors.
※The Title Color feature is a Premium feature. Free users can try it for 10 days.
You can also permanently hide specific colors
You can also permanently hide reminders with specific colors from the list.