In the Timeline Fast Menu I select Show Markers > None, then Show Markers > Blue, for example, but no markers are visible on the timeline.

Is anyone else having this issue? Or has it been reported previously?

Furthermore, when using the Go To Next Marker and Go To Previous Marker, despite the fact that none are visible, it cycles through all of them, regardless of colour. Surely it would make sense for only the (supposedly) visible colours to be navigated to using these commands or, at the very least, have an option to navigate to visible markers only.

My workaround and the moment is to duplicate the sequence, go to marker tool, and delete unwanted markers. But it would be nice if the Show Markers option just worked as intended.

Oh, how I'd love to delete this post, hiding any evidence of my stupidity.

Turns out, when I was hitting None in show markers, it deselected Markers and Spanned Markers in the top of the menu. Only when I reselected either of these, did the desired colour pop up.

As for the moving between visible markers only, I came across this previous forum post describing how this will work if you choose the same settings in the Composer window (https://community.avid.com/forums/t/118124.aspx)

Obviously by assigning this Composer setting (and Timeline View) to a workspace, I am now easily able to switch between various views of markers and move between ONLY the visible markers.

It was good of you to post the solution. It could well help someone in the future solve the same problem.