The Open Interest indicator shows the parameter "Total volume of open positions - SYMBOL_SESSION_INTEREST".

Explanation of indicator colors: 

If the indicator bar is blue, open interest has grown since the bar emergence, if red, open interest has decreased. 

A slight modification in the indicator:

Now, after the first launch, if prev_calculate==0, the indicator will not re-initialize its indicator buffers. The result: for example, we run the indicator on a chart, the indicator worked for a while and then suddenly prev_calculate==0 is received (can be due to connection loss or history errors) - in this case, the indicator will not re-initialize its indicator buffers, but will continue normal operation.