Hi my personal experience was I just got a negative feeling. To be honest it was after either the 1st or 2nd Istikara. I was just think of that thing/I actually just felt really negative and the scary thing was the 2nd time I did it I actually found out something negative/bad that person had done by pure coincidence.
I also did it another time for something different and I only did it once and remember waking up and remembering the dream. I was sure i saw the thing i was praying about/colour red. I'm sure I read somewhere the colour red indicates a no/negative.