Putting this here so folks know how to do it...

- Open the game and go into Mod Manager. Click Mod Editor at the bottom of the screen.
- This opens three windows: The internet (you can close that), a game window (your test area) and the mods Manager application. Alt tab to the mods manager.
- Double click the mod (Firefly Serenity Crew)
- Single click the character you want to modify
- Scroll down the RH side until you get to the heading you're interested in. Most of the options are self-explanatory, and most have drop down menus so you can select something without having to know the coded name for things. It's great!
- Re hair: There are three colours there and I don't know how they interact. Click on a colour to get the picker and choose another colour.
- You should see a red star next to the character name. This means there are unsaved changes. Click save. I don't know how modding other mods works - whether it changes your local copy, or makes a new one... But either way, once the mod changes are saved...
- Click the play icon on the top. The tooltip says "test".
- Alt-tab into the test area and your changed character will have spawned. You can draft them to remove headgear, or move them closer to see what your changes look like (if you want to find better head models for the characters, go right ahead - I got quite bored of trying to find a head model I liked)
- If you're happy, you're done. If you're not happy, you can kill the character (cheat options in the character menu, far right hand tab), alt-tab back to the mod manager, make more changes and retest. You don't have to kill the old one, but I ended up with multiple copies of the same character and forgot which was which, so it just made things easier for me.