Numbers 12.2

I think you are referring to the colored highlighting around the edge of a cell.

No selected cells:

a selected cell from single clicking:

typing the down arrow once:

my highlight color is blue.

The highlighted cell is the selected (or active) cell. If you are not familiar with spreadsheets you may get help by selecting the Numbers menu item "Help > Numbers Help"

You should get a window like this:

then open the sidebar by single clicking the icon to the right of the green dot in the top-left corner. Then choose "Numbers basics"

McBetts,

I do not understand your question. In the interest of helping us help you, please describe what you want to do and what you have tried.

You may post screenshots to help us see what you see.

Describe what you want to do.

What you tried, and expected to happen, and what actually happened

I took a long look through the list of keyboard shortcuts to find something related to your problem and I may have found it, assuming you started in a green cell when you began using the arrow key.

Command backslash (\) turns on/off auto-fill mode. I think you might have turned it on by accident. Turn it off and see if that fixes it. This is also in the menu system as Table->Autofill cells->Autofill.

Glad you figured it out. That is a setting I have never used. Plus I thought you were saying the cells turned green and stayed that way, not that it was highlighting the active cell in green.