… then update the style. (click the icon at top left)
You can change the color of selected objects in the style as well.
Use the last icon (Modeling Settings) on the right, on the Edit tab.
Mihai shows the first icon Edge settings subpanel active (above.)
Because styling the endpoints takes effect not only in segmented lines but everywhere, that is not a style, which could be used permanently. That is to ugly.
To the color:
I have to think about a better color for selected lines carefully. That’s not an easy decision.
Is there someone among you, who uses an own set of colors for the three axis and selected lines?
It is important, that there’s no “color conflict” with other colors, which visualize the many functions in models.