Why are some topic titles gray?

What’s the significance of the fact that some topic titles in this forum are gray rather than black? For example:

I can’t find any explanation of this.

I believe the grey ones are ones that you have viewed, and the black ones are ones that you haven’t viewed. Click on a black one to view it, go back to the topic list, and it will now be grey.

Yes, I think you’re right - thanks!