I coded a Mancala game in Java for a college class this past spring, and I used the Eclipse IDE to write it. One of the great (and fairly simple) visual aids in Eclipse is
For selected word(s) highlight function only, there is also StickyHighlight.
StickyHighlight supports Visual Studio 2010 & 2012.
The automatic highlight is implemented in Visual Assist as the refactoring command "Find References". It highlights all occurences of a given variable or method, but that's not automatic (binded to a keyboard shortcut on my computer).
Here is an exmaple:
In VS 2017, this can be solved by installing the Match Margin plugin.
It appears to be part of the Productivity Power Tools (which might be worth looking at for other features), but surprisingly, installing PPT didn't solve the problem for me, I had to install Match Margin separately.
Check following addins Productivity Power Tools- Displays error in scrollbar and
Highlight selected word
The highlight functionality is conveniently implemented in VisualAssist. In my opinion, they are both must-have.
1) Highlight identifier under editing caret: Options -> Advanced -> Refactoring -> Automatically highlight references to symbol under cursor
2) Highlight search result - in all windows. Works for RegExps! Options -> Advanced -> Display -> Highlight find results
The "error bar" functionality is provided in JetBrains ReSharper. I'm not sure if it does highlighting of references to the currently selected identifier.