On a limited scale with my mod endeavours ive found you can alter existing CTeffects to create your own.
In the ACTOR CLASS BROWSER properties if you scroll down to EMITTERS there listed are almost all (but actually more) than that you can preview in he PARTICLE EFFECTS BROWSER.
In particle effects browser pick an effect you might want to edit to your own tastes eg fire .
look for this effect in the properties emitters listing in ACTORCLASSBROWSER untick the placeableclasses only box !
Select it then right click NEW PACKAGE name it to your taste EG SANDCRAWLER and then give your new effect a name eg BLUEFLAME
Essentially you are creating a subclass of an exiting effect.
Once you have created this you can then edit this new effect without altering your existing effects package, you would then open the default properties of your new effect and there in the cell for EMITTER it will show emitters and within each drop down you can search for and edit its COLOUR.
Some Effects in the CTeffects package you will notice are looped or just "run thru" once. This also can be edited in ADVANCED of its default properties it has LIFESPAN usually set to 0 but you can edit this to say 2 or 3 etc
Eventually you can close unreal ed and remember to save your new package by default it will do so to the Properties folder,But sometimes you might accidentally save it to another folder . if so just move to Properties folder
If you have a problem or it appears not to have saved properly goto the respective folder and look for your new package
by name and remember to use suffix at end .u EG SANDCRAWLER.u
You can add many more new effects in this manner to your existing package..
Remember if you are using Modded custom effects you must include your package.u with your maps or others wont see these effects..