Numbers on iMac Pro: Green frame and cursor issues when moving cursor

A screenshot of what you're seeing might help...

That said, the 'green border' sounds like System Settings -> Accessibility -> Keyboard -> Full Keyboard Access

It's a MacOS feature designed to facilitate screen navigation via the keyboard (e.g. for those that have motor control issues using a mouse, or even just user preference). For most apps it works well, allowing keyboard access to each control, button, field, menu, etc. on screen. However, it conflates with Number's keyboard navigation around a table and kind of breaks the metaphor, until you really get to understand it - for example. with FKA turned OFF, the Tab key moves to the next cell in the row, but with FKA turned on, the OS intercepts the tab key and switches focus to the next table/tab/control.

So check your System Settings to see if that's the issue. If it is, decide whether Full Keyboard Access is beneficial or not to you in Numbers.

If that setting isn't on, please post a screenshot showing what you're seeing in more detail.

Camelot - turning off full key board access helped resolve cursor movements and green box in numbers and pages. Thanks !!

However, there is a "blinking blue or green" line that is still showing up in apple mail once I click on a given message content. Screenshot attached.