Schwanton is correct, never unthread the serger - always tie your new thread to the old thread.
Now, I have accidently unthreaded mine - Singer, it it took an hour to get it correctly threaded. Unfortunately if a thread breaks, my experience, you have to rethread in the correct order...so if thread 1 breaks - you must rethread all (trust me learned the hard way tryng to short cut)
Once threaded correctly - I love my serger. It opens up new avenues for sewing and quilting too.
Hang in there,and very carefully in order follow the color coded chart on the machine. Do not try to short cut, thread the machine in the order specified in the directions. It does make a difference(do not know why, but does).
I can now thead my machine in about 10 minutes if needed, but I use schwanton's suggestion of kntting the new color to the old.