I feel like this might bee a good idea to help clean things up. On top of a whole spectrum of UI designs and such to make these lines a LOT less confusing.
The vertical lines orbital units draw down to the planet are already teamcolored, so why not transit lines Good idea !
Awesome idea that I believe would help greatly with the ability to coordinate tactical movements on interplanetary actions.
It also helps you to know who is a bout to nuke to certain annihilation and multiple other things without having to look for the specific object in transit
Additionally, it'd be cool if the transit lines had some different symbols on them based on what type of thing is transiting, normal like for units, maybe put little arrows on the line for a Nuke or something? just so you can quickly tell what type of incoming you have, and who it's from without losing much time. You could even have a little expandable box on the ui somewhere which shows all incoming and departing transits from the planet you're zoomed in on, a tiny version of the build menu icon for what type of unit, with a little multiplier number in the corner of the icon to show how many (no one wants an endless list suddenly because someone is sending 50 avengers) then the name of the unit written in team colour, or just a coloured bar even, and for super snazziness, you could even have a timer ticking down for the ETA.
This would be very good especially in late game or orbital focused maps... ALL THE GREEN GOING EVERYWHERE! so confusing >.<