This is the first time I'm seeing a red colour beside a queue. What's its significance?
I did around 5 "First Questions" review and that I've done before with a grey symbol too. (1 was a test but again that was with grey symbol too before).
The red dot means that there are 'many' items to review in that queue, it is there to encourage reviewing. The gray dot means that there are items to review.
The precise meaning of 'many' depends on the queue.
For more details see the link provided by Martin How does the review-needed indicator work exactly?