This thread has how to build a lightsaber
And This talks about recoloring saber blades
Basically to make this mod you'd have to do the following:
--Make a number of new saber crystals. However many you want for the mod.
--Add your crystals to ucrystals.2da This makes the saber upgradeable, you can take out the crystal in game, etc.
--Now the fun part... make .uti files of each lightsaber. A short, single, and double for each crystal. So if you want 10 levels of transition, you have to make 30 (?!) Utis. In addition to having all of the inherent upgrades (If Bondar Crystal is in, do this, etc.) You add a bunch of Bonus properties to each lightsaber based on the properties of the crystal in the saber. You then put these as having no requirement to get. What this does is if you have the lightsaber you have the bonuses it grants.
(One of the most confusing things for me when I started was this. When you change the color crystal in a lightsaber, it doesn't change the color of your saber, you get an ENTIRELY new saber of that color and it takes away the old one.)
--Now make the blade colors of each blade. And save them as TGAs.
EDIT: --Forgot, now create a text file using windows. Copy the txi information from a saber in the game into it and save it, then manually change the file extension from .txt to .txi
--Now make MDL and MDX files for each blade by stealing and hex editing an existing blade. In addition to what Achilles says on changing the four references in the mdl, change the first two references to the name of the saber to yours (at least.) At least I'm not sure he says to do that...
--Pause, BREATH (actually, I hope you have been up to this point, that took a while.)
--Now you have to go in and modify Kreia.
--Open up and modify her .dlg making a new dialogue path with conditionals on that you must have found a new saber blade crystal. Have this dialogue path execute a script.
--Write a new script *cringe* that checks to see if you have a lightsaber with this crystal in it. (Or be lazy and make you take it out of the saber.) And if you do have it, check against your alignment. Then take away the current crystal and give you the same crystal different. (The +40 lightside instead of +20 lightside crystals that we made at the start of the game for example.)
--Futz around with sound editing, trying to use existing Kreia voice files to make her actually say what you have her saying in your new dlg path. Realize after six hours of futzing that you can't and give up.
Now, collect your thoughts and...
--Compile the whole thing and make it use TSL Patcher. Cause you're modifying .2da files and you're not going to be inconsiderate enough to make your mod incompatible with stuff like USM.
...And you're done.
Way too much work for me, and that might be the hard way to do it. For examples of color crystals giving you ability bonuses, check out my Exile Item Pack mod. And feel sorry for me. I'm trying to do something similar to this for a new mod. It'll give Handmaiden a "Kinetic Lightsaber". Basically it looks like a lightsaber, but does physical damage (Bao-Dur helped her build a 'force-field' saber) and she gets to use all of her crazy unarmed combat feats with it.
Now that darn thing is so complex I wanna cry.