Change Bars (IDE Tutorial)
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The left margin of the Code Editor displays a yellow change bar to indicate lines that have been changed but not yet saved in the current editing session. A green change bar indicates the changes that have been made since the last File > Save operation.
You can, however, customize the change bars to display in colors other than the default green and yellow. Select Tools > Options > Editor Options > Color. In the Element drop down menu, select Modified Line, then change the foreground and the background colors.