• Yellow – you’ve edited these lines since your last save.  Yellow becomes Green upon saving.
• Green – the lines you’ve edited before your last save.  Save again and Green disappears.

Not seeing it?  Go to Tools – Options Dialog, and on the Text Editor – General page, check the Track changes checkbox.  And now you know how to turn it off =)

Still not seeing it?  Make sure the Text Editor – General page has the Selection Margin checkbox checked. 

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