ideology building coordinated

I believe its not twice the distance, but 50% more is gained.

I think this affects the production malus only.

The text is green when you can add population to a ship from that planet and that is not affected, it is always 6 tiles max

Looks like the penalty by default is 2.5% per tile after 6, so a 50% reduction doesn't extend the range without penalty, it just cuts the penalty to 1.25% per tile after 6.  

I guess it works this way so that if your the Terran's and have the ability for the 50% reduction to shipyards, then get the talent for an extra 50% reduction. you get a 100% reduction meaning all planets become green no matter the distance. kinda nice if you have spread out planets or want to push all your production to the front lines. You can have a fleet of shipyards all together pumping out mega ships to make a new fleet every turn.

The only planets that turn green are those within 6 hexes. They contribute to populating a colony ship. The others are white and contribute to production.

If you use the edit sponsors button on a starport you can see the list of planets sponsoring it, and mousing over the production figures on the right will show a tooltip that shows the distance decay.