I wanted to understand why I see some of the questions in cyan as in the attached image. Thanks in advance.
The questions which are in different color are those ones, which have one of your favorite tags.
- Questions with these tags become highlighted on the front page.
- Questions with new activity are shown on stackexchange.com/filters.
- In the review queues, questions from these tags are shown to you before other questions.
The actual color is different for various sites - it depends on the design and color scheme of the actual site. For example, it is different also here between the main site and meta.
More about adding (or removing) a tag from the list of favorite tags: How do I follow tags?