.:Contrail Editor:.
-by DarkMetal
Basically this lets you select the color that you want the contrail to be and then writes the color in Halo 2's format (weirdly divided floats ftw). Anyways... to my knowledge this works so far. Here are some pics courtesy of MadRoX:





Here's a basic tutorial on using the app:
1. Open a map.
2. Select a contrail meta.
3. Edit the colors or the width to your liking. Take in mind there's more than one chunk, so I put a chunk selector in there.
4. Press the save button.
5. Sign.
That's about it!

Click the picture to bring up a color dialog
CREDITS:
Thanks to MadRoX for the pictures and for testing.