http://www.voupr.com/plugin.php?name=dopplerhostility

Paints ships in the radar red if they are approaching, and green if they are stationary or moving away. Optionally flashes back and forth when the ship is within the proximity alarm's distance.

Display help:
/dopplerhostility help

Toggle plugin:
/dopplerhostility [enable|disable]

Toggle whether ships in prox range blink:
/dopplerhostility prox

Set blink period to N ms:
/dopplerhostility blink_period N

would this then conflict with something like "makefriends"?

MakeFriends resets all hostility/friendly indicators when you change the settings and log in. This will override MakeFriends settings.

Much like in the same way after you've set MakeFriends to keep group members friendly, but then they damage you, they're set hostile by the game.

Yeah, this will conflict with anything else that fiddles with the hostility settings. They shouldn't explode or anything, just whichever one happens to override the function last will control it.

Since it fiddles with hostility settings, it will also interfere with "target nearest hostile". You can use something like TargetButton to get around that.

Messing with that also bungles the AutoFire feature on Android and iOS.